I'm very disappointed that people don't know too much about Remote Play. I guess it's Sony's fault for not educating the public about it, but it seems as if everyone does a doubletake when they're finally enlightened and that just shouldn't be the case.
As for lag; It's very dependent on the upload speed of your PS3's net connection. This will undoubtedly increase over the next few years (it has for the last couple of years), so I still think that PS2 and 3 games will be completely playable within this lifecycle. ALSO, the lag doesn't seem to affect movie/music playback -- the quality, even on the highest, is about as good as VHS, but that's still friggen amazing. And I expect the amount of quality options/adjustments to improve with future firmware updates of the PS3/P.