I have a friend who just upgraded from an old tube TV to a 26" HDTV, and he loves it and thinks it's a much better improvement.
I've been on HDTV's since 2005, starting with those huge ass rear projection models. So I honestly don't remember what playing on a SDTV is like... but I would assume the experience could differ depending on TV, brand of the TV, and what cords you use.
IRON MAIDEN IS MY RELIGION! Gamertag: Demigod Elessar (I was formerly Demigod Tyek on these boards, and as a gamertag)
I'm glad I'm not alone/crazy. I played on my SD TV forever and never had a problem, but when I go to someone's house or something to play I am significantly worse at the game because of their nicer TV's. I have heard everyone tell me it's all in my head and stuff like that but I can FEEL the difference.
I have heard that some nice monitors don't have any lag, though. I recall hearing about the ASUS ones being used for MLG awhile back? I could be mistaken, though. I'd imagine if they were willing to use them at a professional level then they must be pretty damn good.