I have hooked up my rig to my bro's 42" HDTV plasma and the visuals looks alright. I think the res was 1024x768 for a 42" screen thats not good compare to a pc monitor. I play BF2 and I could really see the jagged edges/aliasing and lines as well, even when I set it to 4x AA and even SLi AA. Big pixels are really noticeable during gaming, but if you set like 30 feet from the TV then I guess it fine.
For media though it great as I have played some movies on the pc using the plasma TV. But like I said it won't be as good as a monitor.