Response time is generally less of an issue when looking at higher end monitors, so its moved way down on my list.
A LCD for me needs really nice contrast, and must have very very good black levels. In fact, I recently picked up a new CRT for my gaming system simply because of the black levels.
I also look for resolution, 1280x1024 is fine for me for the most part, but this depends greatly upon the size, for a 19" 1280x1024 will do fine, with higher as a added bonus, anything larger than 19" and the resolution better get a good step up.