I haven't had a person come to my place and NOT see a very noticeable improvement in video quality when I show them the better looking Blu-ray titles.
I also don't follow this arguement that "I already have this on DVD" Then buy films you
DON'T CURRENTLY OWN...wow that seems very difficult
I have purchased a few replacements, but most of the titles I have been buying are all ones that I don't own / always wanted or which are new titles. When DVD came around, don't tell me you were also whining "But I already have this on VHS..." I currently own exactly zero VHS tapes.