Funny thing; I started out with the first MBA and found it to be too hot on my lap and was told by Apple that it was b/c it needed more thermal paste! After (3) trips to someplace in Texas, I asked for a full refund for case, AppleCare, MBA and all the extras I purchased at the Apple Store! The gave me cash too!
Having purchased a new 2014 MBA and no heating issues and stayed with the 13" MBA and notice that it seems as fast as my older MacBook Pro (Classic) 2.5GhZ 640GB. I've researched and demoed the heck out of MBA's 11" & 13" the past few months and liked the size of the 13" MBA b/c the 11" was about $100 cheaper with the smaller screen and I didn't mind the $100 bump. It's a relief to carry the new MBA 13" v. MacBook Pro 15" in my backpack/messenger bag/carryon luggage, after all these years! Didn't really notice a huge weight difference between 11" v. 13" either...
Funny situation, while sitting in class and taking notes on my first MBA, my Professor was very hand-oriented in expressing himself during lectures; and he accidentally hit my MBA and knocked it off my desk, but I was able to catch it as it fell about two feet, just caught it about ONE INCH from impact! lol