I agree with everything in your post Dikmer, especially that a cleric's UI should be unobtrusive. I also put together mine with bits and pieces downloaded from this site.
Things I find most helpful:
1. Group window that includes me in the list.
2. Access to bags and clickies without opening inventory.
3. I'm a mouse-user so having everything important clustered together in one spot is key.
4. Text labels for spell bar and buff list.
5. Everything as small as possible, and transparent if possible, to allow for maximum viewing area.
Eradikate Exorcista
Cleric of Povar