Hi, I am planning to upgrade my OS to Yosemite on my MacBook Air (Mid 2009). From the apple website and other pages I figured out that my MacBook Air 2.1 can be upgraded to Yosemite. What I am concerned about is, whether there will be any disturbing amount of degradation in performance as the machine has 1.86GHz core2Duo processor and 2gigs of memory only. I mostly use my mac to write codes and build app for iOS. My concern lies in the reduced performance. Is Yosemite going to slow my machine to death? Please those of you have installed Yosemite on a MacBook Air 2.1, or lower please share your experience or any issues that you might have faced. TIA.