Great news on these UIBuilder changes! I'm uber-nooba-new so I guess I need to find out where to go sign up for the beta
Most of my work has been based on Zonx's fetish UI core and I guess what I'm doing is "polishing". I'm not as familiar with xml as I'd like to be, though I am able to script (python, php, etc) so actually it not a huge leap. But as a visual tool UIBuilder is just wonderful.
What I'd like to see is a way to copy/paste elements from one running copy of UIBuilder to another. Right now I'm working on 2 themes of the same UI and if I come up with an idea in one, I'd like to mirror it to the other. Right now I just weed through the code, copy, paste in my text editor.