I tried out a few themes at the weekend on misterpoo.com
I liked Cutline and Copyblogger - nice and clean!
BUT Now my site is screwed up in Firefox whilst OK in IE7.
Basically, no matter what theme I switch to, the sidebar (or one/both of the sidebars if it's a 3-col theme) gets pushed to the bottom by Firefox. It looks awful and I don't know what I've done.
I did try to add a favicon yesterday... perhaps this has buggered things?
If anyone has any ideas - I'd be grateful - I'm back off to try and hack it myself...