even with a new cpu you can't run mountain lion so its already limited.
Mountain Lion is overrated. It should have been a software update (10.7.4 to 10.7.5) if anything.
All Mountain Lion does is add useless notifications, airdrop, and airplay but that only works with really brand new comptuers. I actually prefer Snow Leopard and I dislike how Apple is increasingly trying to control what you can do.
Don't fall into the deceit that Apple manipulates its customers that it needs a new computer every 2-3 years. It's all dishonest business practice. Besides, for 95% of users, they don't need all these new features. They could have provided support for many older computers, but they chose not to. It wasn't a hardware issue, it was simply because they did not want to write the drivers for the older ones. It's Apple's new direction in planned obsolescence. Preventing you from upgrading components (everything is soldered) even BATTERIES and pressuring you to buy their new product. Of course, you can buy a battery from them, for like $300, but then you ask yourself, you could sell your computer for $500 + $300 = $800, and only $200 for a new computer.
If you have money to throw away, or are just financially reckless, then you could say that a used car is bad and only brand new is good.