I'm thinking of ordering one for my 13.3" macbook air. Thinking about going for the basic sleeve without the flap - I'll be using it inside another bag. Anyone have one of these that can comment on quality/value? Also, is the case itself rigid or flexible? I had a booq vyper sleeve for my 15" macbook pro, and I loved that thing. I'd get another, but they don't have a customized version for the macbook air.