Just downloaded the book and will be going through it soon and hopefully post a review on my blog and Amazon. One UI that would be interesting to see that I didn’t see in the extensions project would be an expandable radial selector control. This would be useful as a skill/ability selector, possibly a dialog control as well. Something like this.
Clicking on an item in the main wheel could either select it or pop out a set of items under that item.
It would be a pretty complex control of course, but if designed right fairly flexible and usable for several different things. Ideally the items could be a graphic or text.