I've built up a DVD collection for almost 10 years, so I'm not keen on converting (until/unless they stop releasing movies on DVD). At a store I saw clips of Spider-man 2 in a video showing off the quality of Blu-Ray on an HDTV, and it made everything look faker (I can only imagine what older movies look like).
I like having physical copies because I don't like having to back things up all the time. Plus I'm sentimental and like displaying a collection. :P