Perhaps it's my eyesight, but I'd have to admit I can hardly tell the difference in HD and SD
A lot depends on the tv you buy. I have a Samsung 40 inch 7020 which is 1 year old now and you really can tell the difference provided the programme is in HD. I have a friend who has an older Samsung HD model and there is hardly any difference at all. We both use Sky+ boxes.
I notice HD quality more with Sky news in the studio, but a recent shot of Yemen on the news would hardly give HD pundits house room. ITV1 HD is hardly noticeable but BBC HD is sometimes excellent especially wildlife programmes.