I just posted an article on this site concerning the insanity known as converting high-definition movies from HD-DVD or Blu-Ray to Quicktime compatible files. The most annoying thing about the process of doing this conversion is the immensity of the data involved. Typically the process will gobble up 40-60 GB of hard drive space per movie, until you're finished. You can compress down to about an 8 GB file if you want, keeping the surround sound and very good quality video, but I've decided to keep the original video tracks so I can re-convert them in the future, if need be, to a better format.
I'm still working on the end result, though. I want to be able to playback the uncompressed source files in Quicktime, but so far the best I can do is a stuttering playback using Perian—it will try playing the VC-1 encoded video, but do a fairly poor job at it. The best program I've found for doing this is Plex (a media player/interface, like Front Row), but Plex isn't the perfect solution for what I want to do...
I've yet to buy any Blu-Ray movies, simply because the movies and players for them are too expensive; $25 for a movie that I could get for $5-10 on DVD doesn't work for me, and there aren't that many that I'd be interested in anyways. I bought the Bourne Trilogy, Planet Earth, the Mission: Impossible Trilogy and a few other HD-DVDs for a bargain-basement price, and bought an Xbox 360 HD-DVD drive (uses USB 2.0 and plays nice with Mac/PC) for less than 1/10 of it's original price, and I have to say, once you go High-Def, you cringe every time you look closely at DVD playback!