i have 2 mini 9's one running OSX 10.6.4 the other running mint 4 - to be honest I have no problems with either unit.
My kids are now using them and so far both seem happy with their respective OS's - in saying that both my mini's do run 64gig runcore SSD
's with 2 gig ram.
linix mint runs out of the box with only the wireless drivers needed to be downloaded, my eldest (9 yo) loves the wiggly windows and other effects all which seem to run fine. Paige like OSX - in saying that she was upset yesterday cos she wanted to play some flash games and did not know how to download the flash player.
Overall if OSX is causing u drama then I would not hesitate to recommend mint - speed wise for me side by side it's similar to OSX - but then I have a high spec'ed mini 9 with a slower SSD
and less ram you may not see any improvement on your mini when compared to OSX.