I only had OSX installed on mine when I fitted an internal bluetooth module. Enabled it in BIOS, booted up and everything was recognised and worked fine. Magic Mouse pairs and works really well, especially with BetterTouchTool installed :-)
The only issue I have at the moment is coming out of sleep sometimes the bluetooth doesn't come back and appears to take out the WiFi at the same time...
---------- Post added at 01:31 PM ---------- Previous post was at 11:56 AM ----------
It appears that a fix has been found!!!
After reading some advice on another thread I removed the 'Bluetooth DUN' from networking and re-created it. Now my Mini comes out of sleep fine and Bluetooth and Wifi both work again (or at least it seems that way - only put it to sleep 3 or 4 times so far but looks good).
One thing that has been noted about the Magic Mouse is that you may need to click the mouse to get it to reconnect after sleep :-)