Got the leather "envelope" for the wife's 13" Air. She loves it. It has a rugged, tight thick fit, but still feels light and protective. Also, it has a snap, in addition to the little tie thingy.
Also got a version of the same, but different manufacturer, for my father's new 11". He loves it even more. Loves showing it off. His version of the case, however, doesn't have the snap- so it just ties closed- and it isn't as good. The leather, however, is still perfect.