The question for me isn’t whether or not there’s a difference that I might be able to see if I were paying attention to the picture quality, it’s whether the video is sufficiently bad to distract me from what I’m watching. And only hypercompressed macroblocked-to-hell-and-back ancient MPEG1 files or multiply-recopied VHS tapes from the Dark Ages are ever that bad for me. In general, I’m perfectly happy with 480p. Of course, I might just have a higher-than-average immunity to bad video. (Similarly, I can spot tearing if I’m looking for it, but I do have to be looking for it.)