Just ran across this over on CSS PLaY, if you’ve never been over to this site definitely check it out, Stu Nicholls has some awesome stuff. The normal conditional comments I’ve seen, but he poses solutions for Non-IE and an IE 6 or Non-IE conditional comment.
<!--[if !IE]><!--> <h1>You are NOT using Internet Explorer</h1> <!--<![endif]--><!--[if IE 6]><!--> <h1>You are using EITHER Internet Explorer version 6<br /> OR a non-IE browser</h1> <!--<![endif]-->