I'm sorry. i have 20/20 vision and perfect color vision and i just cannot perceive it.
If you stuck two HDTVs side-by-side, one with 1080i blu-ray disc with
HDMI hookup and another with 1080p and the same setup, nope, no diff.
Stick a digital (and good reception) quality
DTV signal on a 25" console and then stick a
HDTV with a 1080p, nope. the screen's bigger that's about it. although it's true that HDTVs have higher resolution so obviously using anything other than
HD or a connection other than
HDMI or
DVI (say use only RF-in) and yea, the picture sucks. but on my SDTVs, even if the signal is whatever, it looks fine. no sucky down-convert and no need to use
HD since all pictures are nice (And the black levels are on par, something that even today LCDs fall behind on)