Current favourite Sass compilation with gulp, it also sucks in bower depdencies

gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var autoprefixer = require('gulp-autoprefixer');
var concat = require('gulp-concat');
var filter = require('gulp-filter');
var streamify = require('gulp-streamify');
var watch = require('gulp-watch');
var bower = require('main-bower-files');
var es = require('event-stream');

var paths = {
  styles: {
    file: 'styles.css',
    src: './scss/styles.scss',
    watch: './scss/**/*.scss',
    dist: './assets'
  }
};

(function() {
  function styles() {
    return gulp.src(paths.styles.src)
      .pipe(sass().on('error', sass.logError));
  }

  function dependencies() {
    var files = bower();
    return gulp.src(files)
      .pipe(filter(['*.css']));
  }

  gulp.task('styles', function() {
    return es.merge(dependencies(), styles())
      .pipe(streamify(concat(paths.styles.file)))
      .pipe(autoprefixer())
      .pipe(gulp.dest(paths.styles.dist));
  });
})();

gulp.task('watch', function() {
  watch(paths.styles.watch, function() {
    gulp.start('styles');
  });
});