Summary
I literally just finished watching the HD DVD on my external XBOX 360 HD DVD drive. Before watching the movie, I was skeptical that a movie filmed in 1982 could actually come anywhere near the clarity of HD. Much to my surprise, the clarity and definition was just amazing. You'll notice details in the film that you hadn't seen before. You can actually see tiny detals on everyones' shirts, sweaters, hair, etc. I just turned the disc over and am watching the plain DVD version; it isn't nearly as clear as the HD DVD version.
The only minor complaint that I have about the disc is that the "Extras" feature (i.e. the interviews of the actors talking about the film) are on the DVD side. However, you can fortunately listen to the director & producer's commentary on the HD DVD side. It's definitely worth listening to because their commentary offers interesting insight for each scene.
I highly recommend this classic! When you see it in HD, it's like seeing it for the first time!