Although I’d vaguely heard of it before, I just tried it out, and it’s great. If you use Firefox, the better gmail extension is a must have! Some of the things are really useful – like Saved searches (I’ve actually written feedback to Google to include this feature) and displaying the unread message count first in the title bar. I like their “Super clean” skin as well (except that it doesn’t skin the Saved searches box).
Here’s a screenshot (click to view large):