I currently am using a 15" Early 2008 non unibody Macbook Pro (upgrade 250gb HD to 750gb, and 2gb RAM o 4gb RAM) I am looking at the current MacBook Air 13" 4gb RAM, 128GB SSD. I'm seeing the spinning wheel a lot more these days (currently on Mountain Lion) I have a 100 off at Bestbuy for Macbook. Anyone go from a 15" early 2008 MBP to a 13" Air? Should I be looking at doing a custom build and adding more RAM or SSD? I think at about 960 out the bestbuy door for the 13" MBA 4GB/128GB seems good, but as with my current Early 2008 MBP I'd like it to last for 5 years or so. Thoughts, suggestions, etc are welcome. Last time I did this was Early 2008 MPB 15" or new UniBody 15" MBP (some deal that made the old gen cheaper was helpful) I'm in no rush as my MBP 15" is running and is my primary machine. Just wondering if I would notice a great increase in performance with the current 13" MBA base.