I always vote in order of Viewsonic, NEC, Samsung, but I bought the Samsung 930B because of the reviews I've read here and it was $50- off at Best Buy. I don't regret it, it's performance is far better than I thought possible and it has this neat setting button that shifts from custom, text, internet, games, sports & movies adjusting brightness and contrast for each. Very handy.
viewsonic makes cheap monitors and their cheap models are pretty crappy. the vx series is good and their professional models are good, but if you're gonna get those cheap 200ish models, they really suck. might as well get a quality 17 incher or like i always say, get a dell. High end Viewsonic is good, NEC, Samsung, Sony, Dell. All good monitors.
Any company that has more than a few models of LCD is going to have some low-end models and some high-end models. Viewsonic, Samsung and the others has some excellent models but they also have cheap ones for people who don't want to or can't spend too much.
The only exceptions may be NEC and Sony which all seem to be expensive.