I have a 7800gtx and I'm currently running at 1900x1200.
The tv is a samsung lnt4071f
Also it looks like about a 1/4inch all around the desktop is cut off on the TV. It looks fine on the monitor but on the TV some of the icons are off the screen.
I know a few that have with various models, but the thing you need to make sure you understand (and I don't think Mark stresses this enough....he should be shouting it on the first line in 72pt text...sorry Mark ) is that having the TV "say" the connection is 1080p/120Hz on it only means that it's taking in 1080p/120Hz.
The TV can still be doing "Frame discarding" or "Frame dropping", etc., "on the way out to the display".
No nVidia (etc.) driver PC side can yield that information, because the PC will never know what the TV is doing internally. The TV can certainly report back that it's taking the 1080p/120 but it'll be throwing away frames in front of you anyway.
You need to visually inspect the results of a test utility, which means actually looking at your screen.
That said, (Mark does stress this enough) always test for 720p/120 if the 1080p fails. Folks in the thread I started on the Sony R550A series have reported that 720p works but not 1080p even though the TV will claim it's taking it in.
And THAT said, because it's an "out-of-spec spec", it's possible that later firmware/hardware revisions will allow higher rates, or even less. Test the TVs the moment you buy them.