There's a lot of information
here at the Widescreen Gaming Forum.
Personally, it seems Dell's 22" would be a TN panel, using 16.2M colors + dithering to get all the colors. That wouldn't be too bad, unless you're in graphic design. Not sure about the 27"; all I know is that it's way out of my price range.
As for Dell's 2007WFP (their older model), it costs more because it uses an I-SPS panel for good all-around colors (if not great) and decent response time. I'd pick it over this new 22" in only for that. Only problem is, the 2007 comes in two panel flavors (what I seem to be seeing as a 'panel lottery'): in I-SPS (good) and S-PVA (IMO, not so good). S-PVA's have terrific color (or, rather, my Gateway FPD2185W did), but they lose dark/black clarity when looking straight on at the screen. Considering I stare straight on at the screen 99% of the time while in front of one... Of course, move to the side, and the problem's solved (about 10 degrees, I think). :/ It killed me to look at Hardforum, considering the red stripe across the screen was darker in the middle. Yay for open box items not having restocking fee at Circuit City!
Anyway, if you need a panel for gaming, I'd probably go for the E228WFP. If you want something with more finesse, the 2007WFP is what I'm looking at. That, or the NEC 20WMGX2.