Does 10.8 Mountain Lion run 32bit and 64bit applications?
OS X was the first operating system to ship as a single install that could boot into either a 32-bit or 64-bit kernel, either of which could run 32-bit and 64-bit applications at full native performance. Starting with Mountain Lion, OS X exclusively uses a 64-bit kernel, which, despite rumours that are circulating, continues to run both 32-bit and 64-bit applications.
Which host applications support 10.8 Mountain Lion (click application for more information)?
AVID Pro Tools - Pro Tools Update 10.3 and higher officially support Mountain Lion
Ableton Live - as of Live 8.3.1 fully supported
Steinberg Cubase - see for compatibility
Which VST plug-ins support 10.8 Mountain Lion?
Currently many developers are still testing with the new OS X 10.8 Mountain Lion, and some issues may arise that may require a software update. At present we have confirmation and separate knowledge base articles for the following developers:
What is the Gatekeeper feature?
The new Gatekeeper feature on the OS X 10.8 Mountain Lion has been put in place to help guard against possible malicious software downloaded from the internet. To do this, the software must be signed and verified by Apple in order to be approved by Gatekeeper.
In general, if you are going to install 10.8 over your current OS, you should be fine.
However, please note that if you are going to do a clean install, you may need to bypass 10.8's new Gatekeeper feature during re-installation of your product(s).