My little brother has a Dell 20.1", and it works pretty well for gaming. The contrast/ghosting aren't quite as good as on my 17", but I don't really notice.
In general, LCD screens have gotten much better than they used to be. I'm using a Compaq 15.4" 1920x1200 laptop screen for research, watching movies, games (rarely, alas), and "defense contracting lumpenproletariat" software development. Works great. No ghosting that I can see.
THG is good, rarely comprehensive for LCD screens, but when they get around to reviewing stuff, they're fairly comprehensive, and as you saw they recently rolled out a "Standard" to evaluate LCD screens; Anandtech I also like. Some of the others are rather questionable (e.g., Hard[OCP]), but generally, you'll do well.
I wouldn't recommend buying something based on an in-store experience. Often their settings are all messed up, and they're piped through some nightmare of a KVM switch with a mile of analog cable. Hell, I've even seen them show off the pricey 1600x1200 20" models on the same 1024x768 desktop feed they send to the cheap ones. "Hey dad, look, this expensive one is really crappy!"