It's not thinner than the MBA 2011. The MBA 2011 has regular MagSafe. Maybe they needed to go thinner for engineering reasons to put other stuff inside, but that seems lame.
With the MBA 2011 the connector sits very low such that simply putting the laptop down on a couch will disconnect the connector in my experience. It's the #1 issue I've had while trying to use an MBA.
If using a thinner connector let Apple fix that problem, that would be quite nice. Of course it's possible that it didn't. I haven't had a chance to try the new thing.
I noticed that, too -- adding a snap-on case to the Air solves that, at the expense of making it slightly thicker. However, I strongly prefer the texture/grippiness of the case, and it protects the laptop from a lot of damage (I still use a sleevecase, but I've had the laptop fall ~3m, cracking the plastic case, and otherwise fine). The cases have little feet on them, too, which raises it up to protect the connectors.
