A lot of these SD v HD discussions are from people trying to convince themselves they don't *need* to move to a HD television. Perhaps if you have an Avant - and you do not want a larger screen - then it's a valid standpoint. However, I have a BV7-40 and ideally would like a 46". SD already looks fairly poor on the 40" and will be even worse on a 46". Gawd knows how it will look on the forthcoming BV7-55.
HD does give a far better picture on a large LCD screen (sharper, stronger colours etc). Plus, the audio is better, too, on Blu-ray.