My nepew's dad have a 52" back projection TV and he was totally sold on HD-DVD once he saw the difference in quality compared to DVD so I'm sure there are people out there who are into HD already. But I don't think there's a lot of people who are rebuying their movies. I think a lot of people have stoped buying DVD movies and are waiting to get their hands on whatever HD format they are going for. BD have an advantage here with Sony Pictures who won't be releasing anything on HD-DVD.
Problems with cinema:
1. Expensive (renting is cheaper)
2. Bothersome to get there and waiting etc
3. There usually are people in the way or you have a bad angle
4. Loads of people making loads of noices
5. You can't pause the movie
6. When you're out of snacks or coke you can't get any more
7. Some movies have annoying breaks in the middle
8. The quality of the film lowers every time it's shown
9. You can't each your dinner while watching
10. Probably other reasons I can't think of at the moment