I know what you're asking, and I'm curious about altering the theme as well. I don't ming the Cingular logos. I don't like the fact that you can't really use a different wallpaper image with it, since the clouds image in the upper and lower bands seem to be separate images (they remain and obscure any personalized wallpaper image). On the 8700c, the band was semi-transparent and worked well with a personalized background.

I also like the way the Cingular theme dumped any added applications into the application folder on the 8700c. The 8800 they all get placed on the home screen.

I still prefer the Cingular theme to most others I've tried.