I've been looking at monitors too. Done a lot of web searching on types of screens, specific brands and have practically driven myself to distraction.
Screen types: there are 3, TN, S-PVA and S-IPS. A TN screen is a decent general all around screen, it's biggest draw is it's response time. Basically this means that action looks good, and games are great on them. However graphics aren't. Everything I've read says stay away from units that have TN panels. S-IPS are considered the best graphics screens, with good off center viewing, which would be important in a 24 or 30 inch screen, the down side is that their response time isn't that great so movies and games don't look so hot. But graphically they are considered by almost everyone to be the best. S-PVA is somewhat between the two. Better color and offcenter viewing than a TN screen, better response time than an S-IPS screen. All of the above is not to say that EVERY S-IPS screen is better graphically than every S-PVA screen. The higher end Apples have come under a lot of criticism lately check out both Tom's Hardware and Andand tech sites.
If you've got deep pockets go with Ezio. Everyone says they are the ones to beat. Unfortunately their screens run upwards of 3000, a bit steep for my wallet. LaCie is almost as good, and just about as pricey. I've read good thing about the Gateway 27 inch, the Dell 27 inch 'true color' (or what ever they call it...make sure you get that one rather than the other Dell) and the Samsung 245T.
Here is a good link for a start: note that it was written before the newest round of monitors came out, and before the problems started showing up on the Apples.
Buying a LCD monitor for photo editing | Void Pointer
NaCl(you can really twist yourself into the ground with this stuff)H2O