What specifically is slow -- touch events, scrolling, transitions, etc? We're working on bug improvements on all of these items so things will get faster, lighter and more responsive as we go. Oh, and work on more platforms (Nokia, Blackberry 5, Windows Phone 7). Feel free to log issues on the Git tracker.

Mostly the animated transitions. I get about 4 frames total for the entire transition. Scrolling is also a little slow for the first few seconds after loading a page, but it quickly reaches normal speed.

I'm not working on any mobile webapp projects right now, but if/when I do I'll be sure to provide more detailed feedback on the issue tracker (if I encounter issues at that time), and otherwise contribute back to the community.

At any rate, keep up the great work! I finally took a detailed look at jQuery UI as a result of seeing this post and there's a very good chance I'll be using it in the semi-near future.