Windows 7 on VMWare Fusion asked twice to "free up 1.2GB for installation" even with 7GB free. Suggest 10GB free on Mac OS X just to give breathing room.
Just let VMWare Fusion pretend it's Vista and use defaults for new VM. You'll know you've got a good beta when you see the red and blue literal beta desktop. Very witty, Redmond. ;-)
- michael silverton