Am I missing it or does 21928 not have the settings menu for configuring what the buttons do? I think it used to be under Settings>Personal>Buttons. Right now, the "Easy Settings" button is not mapped for a single push or for a hold and the "Camera" button is not mapped for a hold. Also, I generally like to set my phone to lock on wake up and only wake up using the power button but I can't find a place to set this.
On another note, have you tried installing any of the default themes on this build? Do they work?
I really like how everything is spaced out and bigger. Makes it a lot easier to use the phone without having to struggle with your fingernail or anything. Only thing I was hoping for that wasn't here were the rounded corners seen in this video:
http://www.youtube.com/watch?v=LhiYQwCIVdI
Very cool beta build though, very nice to leave the stylus even further behind than ever!