Well, I have a 50" plasma 1080p as a monitor. It is a samsung, and it works well. If you do this, do NOT use the d-sub that will probably be on the back of the TV. spend a few extra dollars, and get a DVi to HDMi cable, and use that. Trust me it is worth it.
However, I found out the hard way that TVs aren't great as dedicated PC monitors. The pixels seem to be very far spaced, so there will be black lines between them that will usually be a bother. TVs are meant to be viewed from long distnces, so the picture will be less crisp. TVs will often have dead pixels, which aren't noticeable if used as a TV, so it will not be covered under any warranty. If it has a stuck pixel, it will usually have glass over the screen, so you can't rub it out. Also, if you are like me, near-sighted, you will not be able to find a good angle that is easy on your eyes.
If you are okay with all these things, then I would recommend the 42" westinghouse 1080p monitor.I believe they can be had for under $600 now on tigerdirect, and they have good reviews. The best for this would be a samsung plasma, or a sharp aquos.
If it were up to me, I wouldd go with an aquos.