I've only tried Windows 7 within Mac OS X using VMware Fusion 2.0. Works fair - very low performance but still functions somewhat smoothly whenever max settings are applied. Aero features did not work. Minesweeper crashes and system can't evaluate its own performance.
Overall, I LOVE the FEEL of Windows 7 beta. It feels so much better than Vista did. Vista never caught on to me... it had no "personality". Mac OS X is loveable but the feel isn't quite the same as Windows 7 (although it works much better and faster).
Installation took about 20-25 minutes on my aluminum MacBook 2.0 Ghz Dual Core, 2GB RAM
Here is a video Windows 7 beta booting:
I'm definitely buying it when it comes out - and dual booting with it - I can't wait!!! Only 11 months to wait - grr...