I've been running Windows 8 on MacBook Pro and it has been running fine. When I was running the Developer Preview, I would frequently get hard crashes, especially if I was playing music. I suspected it may have something to do with Boot Camp drivers.
The Consumer Preview has been fine so far. If you trouble installing the Boot Camp drivers, run them under compatibility mode as Windows 7. I had to do that with the 3.0 drivers.
As always, have a good backup of your data.