There have been a couple of issues with Mountain Lion and Pro Tools 10 that have come up that any people wanting to live on the dangerous side then you should be aware of these two problems that have come up.
Single commands may cease to work using Pro Tools 10.2 and lower with Mountain Lion Mac OS 10.8
With Pro Tools 10.2 and lower single key commands such as space bar, enter, “R”, “T”, “B”, “H”, backspace, etc. may cease to function. This occurs when AAX plug-ins are used and after altering an automation state, such as going from latch to read or going in and out of trim automation mode. Avid is working to resolve this issue in an upcoming release that officially supports Mountain Lion Mac OS 10.8. The work around is to close and re-open the session or move the plug-in to another slot.
CoreAudio crash, freeze or SWOD using Mountain Lion Mac OS 10.8
When attempting to playback applications other than Pro Tools that use CoreAudio (such as QuickTime player) with Mountain Lion Mac OS 10.8, a freeze, crash or spinning rainbow wheel may be encountered. This does not occur with Lion Mac OS 10.7.x. With Pro Tools 10.2 and lower this affects LE and HD interfaces.
Avid made a general announcement regarding Mountain Lion on August 9th…
Users of Mac OS X-compatible versions of Avid software product may rest assured that Avid plans to provide support for Apple’s newly-announced OS X 10.8 (code-named “Mountain Lion”) and its new security feature, Gatekeeper, which checks software for the existence of a digital signature that identifies its author. This security measure is meant to protect Mac OS X users from installing unsigned software, including malware, that is typically created by authors who understandably do not wish to be identified.
Avid is in the process of preparing code-signed versions of our applications and plug-ins that are compatible with Mountain Lion. We realise that users will temporarily wish to work with versions that are not yet signed. Unsigned software can trigger warning messages from Gatekeeper which Avid users can easily bypass, then proceed to install and run their software.