I'm using a Samsung Syncmaster 215TW 21" LCD that got pretty good reviews last year. It was priced between $400 and $500, but as always it depends on where you buy it. At work I use its 17" cousin, which likewise has a good picture, but feels very tiny in comparison.Samsung's 215TW Product Info
When I first got it, I experienced a lot of shearing in 3D games, but an updated monitor driver from Microsoft fixed 99% of the problem. It was a good reminder that monitor drivers are almost as important as video drivers nowadays.
I get great contrast, true black even in a dark room, and awesome colors. It also rotates for portrait view, which is great for PDFs and other page-oriented documents. Games look great so long as I can play them at 1024x768 or better resolution. I almost need to wear sunglasses if I have Bloom enabled in NWN2, but on my monitor the game looks better without Bloom (helps performance slightly as well.) I have the same issue with Half-Life 2: Episode 2 with HDR enabled. In a way it's kinda cool, I get blinded by bright lights just as in real life. Of course, the monitor lets you turn the contrast down a notch if it's too much, but I usually just turn off HDR/Bloom since the games are plenty bright to begin with, at least on my LCD.
Word and Excel love the extra real estate, as do my programming tools. I can compare documents side by side (or flip the screen and compare top and bottom), while keeping the documents at a very readable zoom level.
NVidia's video drivers can automatically preserve the aspect ratio for games that don't support wide-screen resolutions. Thus if I play at 1280x1024 or 1024x768 I get black vertical bands on each side of the screen image. This keeps the images in such a game from looking stretched out. With 3D games that's less of a problem. Samsung provides software that preserves the aspect ratio of such games in case your video drivers don't offer that option.
I recommend reading several tech reviews before you decide to spend your money. I did, and I don't regret my purchase. It's an 'obsolete' 60hz monitor, but the quality is high enough that I won't need to upgrade for another year or more.