Just the fact that you have more control over the permissions you give to apps makes it worth it for me.

* If an app wants to access your contacts, you can choose which contacts, and you can choose to feed them a "fake" list (which is an empty list). Same for storage.

* You can choose not to give network access to an app, and the system will tell the app that there is no signal all the time.

The other very nice feature is that the Google Play Services and Play Store aren't running as system apps (i.e. they don't have root access): they just run like any other app. So you can choose not to share your contact list with them, for instance.