At first glance, Mountain Lion looks like an identical twin of its predecessor, OS X Lion. Upgraders from Lion will face an almost flat learning curve, because almost every feature they`ve learned to use works in almost exactly the same way as before. But Mountain Lion unobtrusively slots in dozens of new featuresApple counts two hundred of themthat enhance sharing, messaging, cloud-based synchronization, security, Web browsing, instant notifications, and accessibility."
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips