Is there ever a reason to go for the smaller factor? At work, we got 13" macbooks, and I wish we'd gotten the one-size-up ones. I'm a reasonably healthy human being, and can easily carry the slightly larger version - not that I do, because 99% of the time it's sitting on my desk, anyway. When I'm away from my large monitor, it irks me that I don't have more screen real-estate.