I debated about whether to upgrade to Yosemite on my MacBook Pro. I was worried about how it would perform on such an old computer. I finally decided to give it a try and, worst case scenario, I would have to buy a new laptop (but hoping to wait until new Air ones are out). It took FOREVER to download and install. It was unbelievably slow and jerky and I was regretting big time my decision. Then I did a permissions repair and there were a LOT of changes. I restarted and, boy, what a difference. Just thought that I would post my experience in case there are any others out there debating whether or not to install Yosemite on an old machine.