Hey Wimbo!
I bought a 21" last fall and had the same questions.
Something I did, and strongly recommend for you, is seeing the monitors you might be interested in with your eyes before you buy. Monitor specs are notoriously misleading and don't begin to address a lot of the issues that will determine if you love or hate your monitor. Given what you will spend for a quality 21", it is well worth your time to do an eye test before you buy.
I had the NEC FE1250+, Sony G520, Viewsonic P225F and Mitsubishi 2060U on my list. It took a few weeks to track them all down, but in the end I picked the Viewsonic. The Sony had the worst picture quality of these four. The color was good but the text quality was notably fuzzy. It wasn't a horrible picture but the Sony had the second highest price and the picture quality I saw didn't come close to justifying that kind of money. The NEC had better text than the Sony but the color wasn't as good as the Viewsonic and Mitsu. It was the lowest priced of my four, and if my budget only went to $500 this would have been the clear winner.
The performance of the Viewsonic and Mitsu was very close. The Mitsu was a little better in text and color quality, but I didn't think it was significantly better to justify its $200 higher price. I've been using the P225F for almost four months and I already think its the smartest investment I've ever made in my computer system.
Hope this helped.
BHD