Nothing but problems. I want to believe that this is the future of Android messaging, but it's a terrible pile of bugs, garbage code by useless programmers, and is yet another embarrassing Google product. Bizarre errors relating to RCS (doesn't even work most of the time), failure to send messages, failure to enter RCS/chat when both people have it installed/ configured, and failure to use many of its own services/ features. I've done all of the troubleshooting with no effect.