I have gotten Mountain Lion (Developer Preview 3) installed on my Mac Pro 1,1 in VMWare Fusion. I had to do a fix to get VMWare tools to install without a kernel panic but from what I can tell it's working ok. I allotted 4 processor cores, initiated 3d graphics, and allotted 8GB of RAM to the VM. I find it ironic that my Mac Pro isn't (officially) allowed to boot 10.8 but it runs in a VM. Here's a link to the fix: http://www.robservatory.com/?p=809 EDIT: While it's running without crashing, I'm noticing that it's not running really smoothly. I'm sure the fact that VMWare Tools isn't compatible yet and that it's running alongside 10.7 doesn't help. Regardless, I still found it interesting.