¡Aprendiendo sobre Ioc y Repositorios y atrapado en el último obstáculo!

Suponiendo que estoy validando la entrada, ¿cómo paso los mensajes del Validador dentro del repositorio al controlador?

UserRepository

interface UserRepository {
    public function all();
    public function create($input);
    public function findById($id);
}

Sentry2UserRepository

class Sentry2UserRepository implements UserRepository {
...
public function create($input) {
        $validation = Validator::make($input, User::$rules);
        if ($validation->passes()) {
    Sentry::createUser( array_except( $input, ['password_confirmation']));

            // Put something here to tell controller that user has been successfully been created
            return true;
        }
        else {
            // pass back to controller that validation has failed
            // with messages
            return $validation->messages(); ?????     
        }       
...

Mi UserController

UserController extends BaseController {
    ...
    public function postRegister() {
    $input['first_name'] = Input::get('first_name');
    $input['last_name'] = Input::get('last_name');
    $input['email'] = Input::get('email');
    $input['password'] = Input::get('password');
    $input['password_confirmation'] = Input::get('password_confirmation');


        // Something like
        if ($this->user->create($input)) {
            Session::flash('success', 'Successfully registered');
            return Redirect::to('/');
        }
        else {
            Session::flash('error', 'There were errors in your submission');
            return Redirect::to('user/login')->withErrors()->withInput();
        }
    }
    ...
}

Sólo 1,5 semanas en Laravel, por favor, sea fácil conmigo.