I'm watching a lot of movies in 720 and 1080 lately. Sometimes it's great (e.g. Wizard of OZ 720), sometimes it's not. Because you see all the details movies don't feel that real anymore. (Which isn't a problem in Wizard of Oz - you now that most of the background is painted ;) ) In Lord of the Rings you can see a lot of the film grain which is often disturbing when you see the perfect CG sequences without grain a few seconds later. Sin City feels cheap in 1080.
You recognize bad focus easily, I think there's a scene in Alien or Aliens where Ripley is out of focus a whole scene - which is disturbing in hd.
- By the way you will find bad focus in nearly every movie - except madagascar and other cg movies.
I still love the movies but often I was just looking onto details which destroyed fantasy in some kind of way because you could see that the rock was not a real one, or the snow isn't real, textures in the background in Sin City are like in an old computer game and so on.
I think more detail isn't always good. Maybe that's a reason why nobody wants blue ray - I know I don't really need it, DVD is cheaper and the resolution is just fine. Exceptions are CG movies and documentaries about nature and sport coverage.