The pre-release does work, but to me it didn't feel like
anything was actually changed (although I only tried Mario 64 and Mario Kart 64). Super Mario 64 played the same as it did on R7. I got those amazing 30+ framerates people have described, but they were only on the screen were your course objectives were displayed. During actual gameplay the fps was still about 10. If you really want to try it, it is safe to do so, but i'd wait for the real R8 to come out.