I currently own a basic model 15 inch 2.4 Core i5 with 4GB ram that is a little less than a year old. I do have the option of selling this back and upgrading to the the equivalent model that just came out. Should I? Will there be noticeable processor speed/battery performance with the newer model? Or is just really about Thunderbolt and a high def camera and not really much else of a noticeable difference. Anyone else in this same boat thinking about upgrading?