I have a mini 9, it has been running OS X for over a year with 0 problems. I started with 10.5.6 and am current with 10.6.3. Much easier to hackintosh now than it was a year ago, and much cheaper.
It runs rock solid. The only issues I have ever had were stupid things I caused, but they were easily fixed.
Mini 9 | OS X 10.6.7 | NBI 20100616212351| BIOS 05 | 32 GB Runcore | 2 GIGS RAM
10V | OS X 10.6.7 | NBI 20100616212351 |BIOS 06|160 GB|1 GIG RAM| 6 Cell Dell Battery
Back up Mini 9| OS X 10.6.7| NBI 20100616212351| BIOS 05 | 32 GB SuperTalent | 2 GIGS RAM