SideBySide
The comment style so good we had to use it ourselves

SideBySide is straightforward, clean, and won’t draw any attention away from your content. When we say we use it ourselves, we’re serious — visit the blog and leave a comment to see it in action..
All you need to do is drop a folder into your theme and add a single line to your functions.php file, and you’re good to go.
Features
- Support for threaded comments (WP 2.7+)
- Trackback list below the comment list
- Clean HTML and CSS, easy to tweak
- Easily incorporate into any themes you’re using right now!
- Access to all future upgrades
Installation
The installation procedure is pretty painless.
- After download the
ZIP, unpack it. - Rename your theme’s
comments.phpfile tocomments-old.php. This is just to protect the theme from any changes we’re making. - Copy over our
comments.phpand the/sidebysidefolder into the root of your theme. - Paste this line into your theme’s
functions.phpfile:require_once(TEMPLATEPATH . '/sidebyside/functions.php');
Note: These instructions, and others, are included in the ZIP file’s readme.txt file. Look over it for more help.
Purchase details
This comment style, a ZIP file containing the PHP files and CSS to make it happen, is all yours for only $7. The files are licensed under the GPL. You are free to do with it what you please.