A friend of mine is looking to sell me a Macbook Air 2,1 A1304 MB543LL/A for $400. I currently have a Macbook White Unibody 2.26GhZ 2GB 250GB HDD that works great -- just looking for something smaller for my traveling. Is $400 a good price for the Air he's selling? Should I go for it? Will I notice slower processing speeds between his Air and my current Macbook?