For me, one thing HD brought that made upgrading from SD more exciting was the widescreen format (plus the space saving flatness). Since I already have a widescreen flat TV, just bumping up the resolution on it isn't nearly as exciting as the jump from my old CRT TV.
I have no doubt that I will eventually have an Ultra HDTV, but I won't be upgrading because of it like I did HDTV.
