Is AWESOME looking. I just grabbed it, so no real feedback on it yet, but holy shit the interface is fantastic!
Info on grabbing it is in this thread. If you're running Windows, there's an option for a portable install which (I believe) should make it so that it doesn't effect your existing Reaper 3 install. If you're on OSX, just put in a different folder.
Ohsnap. This is aces!