Although I haven't gotten my hands on one, the nice thing about it seems to be that while it's slim, it does offer more storage than a laptop sleeve, with a few pockets on the inside and one on the outside for storing the Air's AC adapter and charging cable.
The downside is the price. The base price for a CitySlicker that stores the 11-inch MacBook Air is $129; the 13-inch model goes for $139 (it is made in San Francisco). On top of that, you then you have to pay extra for a handle and a shoulder strap if you want them. But hey, a bunch of folks over at Facebook will be able to afford three or four of these along with matching MacBook Airs once the company goes public.