Been using the Waterfield sleeve for about 3 weeks now and loving it for the awesome craftsmanship and design, protects my Air inside my work bag consistently. Also, use the Civilian Lab case that I just received about 2 weeks ago. Also a good case in my honest opinion.
Have been through the In Case Neoprene Sleeve (didn't like it too much, and still have it up for sale for anyone that's interested).
Been through the UKWrappers Alcatarana Grey Sleeve (didn't like it too much, and also have it up for sale for anyone that's interested).
Also have the Incipio Metal Grey Sleeve (didn't like it too much as well, and still have it up for sale for anyone that's interested).
First case that I ever had was the ManilaMac which I sold to a fellow MacRumors member here, so rest assured, I've got good feedback on this forum.
If interested in any of my cases, prices are decent and not extravagant. PM me for details if you are interested.