I have the exact same combo your talking about, the 6800GT does well, HL2 will run fine at 1920x1200 with no AA and low AF and look great; WoW doesn't run widescreen, its streched so you may want to run proper aspect ratio 1600x1200 with black bars on the side and have a larger picture then a 21" CRT and it will look great also; BF2 can run WS sort of, but I would run it at 1600x1200.
Go to http://www.widescreengamingforum.com/forum/
to read up on WS gaimng.
I'm loving this monitor, even when in aspect ration mode (black bars) its fantastic and the bars are dark black like the bezel (you won't even notice them).
I came from a 21" Sony CRT which is a great monitor and the 2405W is a couple of steps up, I think you'll like it.