Zen theme themes theming themeing

Hey, just general question about theme development: is anyone here using Zen? I've just started using it for a very specific project. I have an experienced Web dev who is helping me build the site and we spent some time poring over Bartik and Stark before settling on Zen. (We needed a balance between the pre-defined structure of Bartik and the very spartan nature of Stark.)

I'm hoping to compare notes with those who've got some experience with Zen.
Thanks!

-Michael