I have VMC and TMT running now on Vista64. BluRays ripped to folder structure and play back fine.
I also am experimenting with MediaPortal and ffdshow on Vista32. I also have MediaPlayerClassic and TMT installed on this system. I have BluRays ripped to ISO and am mounting them with Virtual Clone Drive. I don't have it down to a single click start yet but the movies do play. I see no difference in quality between the two methods/programs.
I like the MediaPortal look better but it takes more work to set it up. I'm still working my way through the learning curve on this one. If you figure it out, post back.
Good luck with your setup.