Deserta is a fixed-width, 2 column theme with a right hand sidebar, enabled for widgets - it's got a picture of a desert on it... (Morocco, I'm told)
The comments are gravatar-enabled and will work whether you're using WP2.5 or lower. There's also separation of user comments from pingbacks/trackbacks.
It is compatible with WP 2 upwards, including 2.5 and 2.5.1 The theme has been tested on Firefox 2, Internet Explorer 6,7 and Opera 9.
Link: Deserta Free WordPress Theme
Demonstration: Deserta
Download: Deserta WordPress Theme - deserta.zip - deserta.tar
Release Notes:
This theme is not sponsored.
Released under terms of GPL v2.