If you're going to play something on HD, better just put a check mark on everything (or just check 720 as well), lest your game might be downscaled back to 480p if it doesn't support 1080 if you're not using a huge ass screen.
Edit: I meant playing a game in 1080i/p on a PS3.
Edit: I meant playing a game in 1080i/p on a PS3.