Apple: Check before you upgrade to Mountain Lion, Application compatibility Table
Things to watch out for before Installing
& upgrading OS X Mountain Lion
Mountain Lion is here, well later today... but are you ready to update your system? See below some useful information and tips how to go about it and play it safe.
OS X Mountain Lion brings a lot of great things from iPhone, iPad, and iPod touch to the Mac. You can send iMessages. Get your Mac in on Game Center. Receive notifications. And more. And with iCloud, now your Mac works even better with your iOS devices. Watch the video
1) Verify System Requirements and Check Compatibility
2) Check App Compatibility
If you’re already running OS X Lion (10.7) then you probably don’t need to worry much, but for those who are upgrading to Mountain Lion from Snow Leopard, there’s a good chance that some apps don't work. (See the very useful LINK below)
3) Most important of course and this goes without saying, is your Backup.
For more info and details please CLICK HERE
Check the App Compatibility Table: