The below examples use the new form API introduced in RC3.

pw-change.template.html

<form class="container" [formGroup]="pwChangeForm">
    <label for="current">Current Password</label>
    <input id="current" formControlName="current" type="password" required><br />

    <label for="newPW">New Password</label>
    <input id="newPW" formControlName="newPW" type="password" required><br/>
    <div *ngIf="newPW.touched && newPW.newIsNotOld">
        New password can't be the same as current password.
    </div>

    <label for="confirm">Confirm new password</label>
    <input id="confirm" formControlName="confirm" type="password" required><br />
    <div *ngIf="confirm.touched && confirm.errors.newMatchesConfirm">
        The confirmation does not match.
    </div>

    <button type="submit">Submit</button>
</form>

pw-change.component.ts

import {Component} from '@angular/core'
import {REACTIVE_FORM_DIRECTIVES, FormBuilder, AbstractControl, FormGroup, 
    Validators} from '@angular/forms'
import {PWChangeValidators} from './pw-validators'

@Component({
    moduleId: module.id
    selector: 'pw-change-form',
    templateUrl: `./pw-change.template.html`,
    directives: [REACTIVE_FORM_DIRECTIVES]
})

export class PWChangeFormComponent {
    pwChangeForm: FormGroup;

    // Properties that store paths to FormControls makes our template less verbose
    current: AbstractControl;
    newPW: AbstractControl;
    confirm: AbstractControl;

    constructor(private fb: FormBuilder) { }
    ngOnInit() {
        this.pwChangeForm = this.fb.group({
            current: ['', Validators.required],
            newPW: ['', Validators.required],
            confirm: ['', Validators.required]
        }, {
            // Here we create validators to be used for the group as a whole
            validator: Validators.compose([
                PWChangeValidators.newIsNotOld, 
                PWChangeValidators.newMatchesConfirm
            ])
        );
        this.current = this.pwChangeForm.controls['current'];
        this.newPW = this.pwChangeForm.controls['newPW'];
        this.confirm = this.pwChangeForm.controls['confirm'];
    }
}

pw-validators.ts

import {FormControl, FormGroup} from '@angular/forms'
export class PWChangeValidators {

    static OldPasswordMustBeCorrect(control: FormControl) {
        var invalid = false;
        if (control.value != PWChangeValidators.oldPW)
            return { oldPasswordMustBeCorrect: true }
        return null;
    }
   
    // Our cross control validators are below
    // NOTE: They take in type FormGroup rather than FormControl 
    static newIsNotOld(group: FormGroup){
        var newPW = group.controls['newPW'];
        if(group.controls['current'].value == newPW.value)
            newPW.setErrors({ newIsNotOld: true });
        return null;
    }

    static newMatchesConfirm(group: FormGroup){
        var confirm = group.controls['confirm'];
        if(group.controls['newPW'].value !== confirm.value)
            confirm.setErrors({ newMatchesConfirm: true });
        return null;
    }
}

A gist including some bootstrap classes can be found here.

import { Component } from '@angular/core';
import { Router , ROUTER_DIRECTIVES} from '@angular/router';
import { NgForm }    from '@angular/forms';

@Component({
    selector: 'login',
    template: `
<h2>Login</h2>
<form #f="ngForm" (ngSubmit)="login(f.value,f.valid)" novalidate>
    <div>
        <label>Username</label>
        <input type="text" [(ngModel)]="username" placeholder="enter username" required>
    </div>
    <div>
        <label>Password</label>
        <input type="password" name="password" [(ngModel)]="password" placeholder="enter password" required>
    </div>
    <input class="btn-primary" type="submit" value="Login">
</form>`
   //For long form we can use **templateUrl** instead of template
})

export class LoginComponent{

    constructor(private router : Router){ }

    login (formValue: any, valid: boolean){
        console.log(formValue);
        
        if(valid){
            console.log(valid);
        }
    }    
}

For live demo click..

App index ts

import {bootstrap} from '@angular/platform-browser-dynamic';
import {MyForm} from './my-form.component.ts';

bootstrap(MyForm);

Custom validator

import {Control} from @'angular/common';

export class CustomValidators {
  static emailFormat(control: Control): [[key: string]: boolean] {
    let pattern:RegExp = /\S+@\S+\.\S+/;
    return pattern.test(control.value) ? null : {"emailFormat": true};
  }
}

Form Components ts

import {Component} from '@angular/core';
import {FORM_DIRECTIVES, NgForm, FormBuilder, Control, ControlGroup, Validators} from '@angular/common';
import {CustomValidators} from './custom-validators';

@Component({
  selector: 'my-form',
  templateUrl: 'app/my-form.component.html',
  directives: [FORM_DIRECTIVES],
  styleUrls: ['styles.css']
})
export class MyForm {
  email: Control;
  password: Control;
  group: ControlGroup;
  
  constructor(builder: FormBuilder) {
    this.email = new Control('', 
      Validators.compose([Validators.required, CustomValidators.emailFormat])
    );
    
    this.password = new Control('',
      Validators.compose([Validators.required, Validators.minLength(4)])
    );
    
    this.group = builder.group({
      email: this.email,
      password: this.password
    });
  }
  
  onSubmit() {
    console.log(this.group.value);
  }
}

Form Components HTML

<form [ngFormModel]="group" (ngSubmit)="onSubmit()" novalidate>

  <div>
    <label for="email">Email:</label>
    <input type="email" id="email" [ngFormControl]="email">
    
    <ul *ngIf="email.dirty && !email.valid">
      <li *ngIf="email.hasError('required')">An email is required</li>
    </ul>
  </div>

  <div>
    <label for="password">Password:</label>
    <input type="password" id="password" [ngFormControl]="password">
    
    <ul *ngIf="password.dirty && !password.valid">
      <li *ngIf="password.hasError('required')">A password is required</li>
      <li *ngIf="password.hasError('minlength')">A password needs to have at least 4 characterss</li>
    </ul>
  </div>

  <button type="submit">Register</button>

</form>

This example uses Angular 2.0.0 Final Release

registration-form.component.ts

import { FormGroup,
    FormControl,
    FormBuilder,
    Validators }              from '@angular/forms';

@Component({
    templateUrl: "./registration-form.html"
})
export class ExampleComponent {
    constructor(private _fb: FormBuilder) { }

exampleForm = this._fb.group({
    name: ['DefaultValue', [<any>Validators.required, <any>Validators.minLength(2)]],
    email: ['[email protected]', [<any>Validators.required, <any>Validators.minLength(2)]]
})

registration-form.html

<form [formGroup]="exampleForm" novalidate (ngSubmit)="submit(exampleForm)">
    <label>Name: </label>
    <input type="text" formControlName="name"/>
    <label>Email: </label>
    <input type="email" formControlName="email"/>
    <button type="submit">Submit</button>
</form>

app.module.ts

Add these into your app.module.ts file to use reactive forms

import { NgModule } from '@angular/core';
    import { BrowserModule } from '@angular/platform-browser';
    import { FormsModule, ReactiveFormsModule } from '@angular/forms';
    import { AppComponent } from './app.component';
    @NgModule({
      imports: [
        BrowserModule,
        FormsModule,
        ReactiveFormsModule,
     ],
    declarations: [
    AppComponent
     ]
  providers: [],
  bootstrap: [
    AppComponent
   ]
  })
export class AppModule {}

app.component.ts

import { Component,OnInit } from '@angular/core';
import template from './add.component.html';
import { FormGroup,FormBuilder,Validators } from '@angular/forms';
import { matchingPasswords } from './validators';
@Component({
    selector: 'app',
    template
})
export class AppComponent implements OnInit {
    addForm: FormGroup;
    constructor(private formBuilder: FormBuilder) {
    }
    ngOnInit() {
  
    this.addForm = this.formBuilder.group({
            username: ['', Validators.required],
            email: ['', Validators.required],
            role: ['', Validators.required],
            password: ['', Validators.required],
            password2: ['', Validators.required] }, 
          { validator: matchingPasswords('password', 'password2')
        })
    };

addUser() {
        if (this.addForm.valid) {
            var adduser = {
                username: this.addForm.controls['username'].value,
                email: this.addForm.controls['email'].value,
                password: this.addForm.controls['password'].value,
                profile: {
                    role: this.addForm.controls['role'].value,
                    name: this.addForm.controls['username'].value,
                    email: this.addForm.controls['email'].value
                }
            };
          console.log(adduser);// adduser var contains all our form values. store it where you want 
            this.addForm.reset();// this will reset our form values to null 
        }
    }  
}

app.component.html

<div>
  <form [formGroup]="addForm">
   <input type="text" placeholder="Enter username" formControlName="username" />
   <input type="text" placeholder="Enter Email Address" formControlName="email"/>
   <input type="password" placeholder="Enter Password" formControlName="password" />
   <input type="password" placeholder="Confirm Password" name="password2" formControlName="password2"/>
   <div class='error' *ngIf="addForm.controls.password2.touched">
    <div class="alert-danger errormessageadduser" *ngIf="addForm.hasError('mismatchedPasswords')">                                  Passwords do not match
  </div>
</div>
<select name="Role" formControlName="role">
    <option value="admin" >Admin</option>
    <option value="Accounts">Accounts</option>
    <option value="guest">Guest</option>
</select>
<br/>
<br/>
<button type="submit" (click)="addUser()"><span><i class="fa fa-user-plus" aria-hidden="true"></i></span> Add User </button>
</form>
</div>

validators.ts

export function matchingPasswords(passwordKey: string, confirmPasswordKey: string) {
    return (group: ControlGroup): {
        [key: string]: any
    } => {
        let password = group.controls[passwordKey];
        let confirmPassword = group.controls[confirmPasswordKey];

        if (password.value !== confirmPassword.value) {
            return {
                mismatchedPasswords: true
            };
        }
    }
}

FormComponent.ts

import {Component} from "@angular/core";
import {FormBuilder} from "@angular/forms";

@Component({
 selector: 'app-form',
 templateUrl: './form.component.html',
 styleUrls: ['./form.component.scss'],
 providers : [FormBuilder]
})

export class FormComponent{
  form : FormGroup;
  emailRegex = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;

  constructor(fb: FormBuilder) {

    this.form = fb.group({
      FirstName : new FormControl({value: null}, Validators.compose([Validators.required, Validators.maxLength(15)])),
      LastName : new FormControl({value: null}, Validators.compose([Validators.required, Validators.maxLength(15)])),
      Email : new FormControl({value: null}, Validators.compose([
        Validators.required,
        Validators.maxLength(15),
        Validators.pattern(this.emailRegex)]))
    });
  }
}

form.component.html

<form class="form-details" role="form" [formGroup]="form">
    <div class="row input-label">
      <label class="form-label" for="FirstName">First name</label>
      <input
        [formControl]="form.controls['FirstName']"
        type="text"
        class="form-control"
        id="FirstName"
        name="FirstName">
    </div>
    <div class="row input-label">
      <label class="form-label" for="LastName">Last name</label>
      <input
        [formControl]="form.controls['LastName']"
        type="text"
        class="form-control"
        id="LastName"
        name="LastName">
    </div>
    <div class="row">
      <label class="form-label" for="Email">Email</label>
      <input
        [formControl]="form.controls['Email']"
        type="email"
        class="form-control"
        id="Email"
        name="Email">
    </div>
    <div class="row">
      <button
        (click)="submit()"
        role="button"
        class="btn btn-primary submit-btn"
        type="button"
        [disabled]="!form.valid">Submit</button>
    </div>
  </div>
</form>