One of the big UI changes this enables is a persistent floating action button that’ll allow you to easily start conversations, as well as an improved contacts list. We also get improved attachments support, so there’s less poking you have to do to attach one or more photos or video.
Google has also greatly improved not only app performance, but the speed and reliability of incoming and outgoing messages. It should now be on par with any typical SMS client. These improvements also bring us improved battery life, something that’s always nice.
Other changes include Android Wear support, the ability to receive and reply to MMS messages in Hangouts using Google Voice, and — wait for it — the return of custom status messages!