Maybe it's just because I didn't grow up with it, but I find it very hard to do anything in the same room as a TV. If I'm visiting somebody who leaves it on all the time, I even find conversation difficult at times.
I'm another both. The armchairs downstairs are really comfortable and it's a good use of time. However, as the PB is in for repairs (or *crosses fingers and hopes* replacement by MBP), it's DS while TVing (oddly enough, I don't play DS games on it much - Minesweeper )
Both at once with a slight edge to TV, I can't be on the computer without the TV going it gets to quite and when I'm not on the computer the TV is still on.