I personally don't like "bloating" my sites with many different plugins if I don't have to, that's why I use Jetpack.
There are many great features and here are some of them:
- Mobile Push Notifications (Receive notifications on your Apple device)
- WordPress.com Stats
- Jetpack Comments (comes pretty handy)
- Subscriptions (who doesn't need this?)
- Extra Sidebar Widgets (Theme doesn't include enough widgets? no problem! add more with Jetpack in seconds)
- Sharing (socialize your site with ease)