I was think of switching from my 2009 MacBook Pro 5,2 (2.8ghz c2d) to a 2013 Core i5 Macbook Air 6,2 - mostly for the portability. I currently use my Pro mostly for Mail, MS Word and MS Excel, and also Skype and Dropbox - usually all at the same time with many, many files open simultaneously - plus occasionally Photoshop Express for some basic photo manipulation and Open Office. I also sometimes use an external monitor as a second screen. Would a Macbook Air 2013 Core i5 (i5-4250U / 4GB Ram) be OK handling this lifting, and would I be losing anything in the switch other than the screen real estate? Also, is the Macbook Air ram user upgradable? Thanks in advance..