I have been running osx 7 on all our madmapper machines until now because accordingly to cinebench (v11.5) the gpu performance drops between 10 - 20% when changing to mountain lion. Maybe it is just cinebench. I know that v15 was released recently.
Making tests I actually learned that osx 10.7.4 was the version showing best gpu performances (with cinebench)
But. No turning back now. New hardware means new minimum OS install. The new mac pros seems like a very interesting companion for madmappr doing multi screen setups (past 4 projectors)