All the games I play support 1920x1200.
Call of Duty
Lord of the Rings Online
Dawn of War 2
I played the Crysis sp, and that supports it. I play ut3 and fc2 rarely. Those both support it. 1920x1200 is supported by pretty much all the recent pc games, and it is probably more standard than 1080p.
I have a computer hooked up to a 52" 1080p tv in the basement, and I had to mess around in the Nvidia control panel to get stuff to display right, so, from my experience, 1080p is worse. Although, this was probably because it was a tv as opposed to a monitor to be fair.
Who really watches 1080p movies on their computer anyway? Most people don't have bluray drives, and 1080p movies are so big that most people wouldn't get them the other way. Even if you are doing it, who cares about some small black lines at the top and bottom? They blend in.
Still, they both are good resolutions. I just don't want this dude to be scared away from 1920x1200 because of what you said. I agree though, dual monitors could be a good idea.