I pre-ordered Tom Bihn Cache. The one I got initially was a bit too tight. (probably they had to make the case without having the Air?) I contacted them, they addressed the issue, sent me a replacement with more relaxed fit and let me keep the first one. I'm happy with their customer service.
The flap tacks in very nicely. MBA's hinge part is fully covered by the flap, and the foam padding is a bit denser than Incase sleeves that I had for older MBA 13" and MBP 13" (the incase ones might be broken in over time though).
I, too, am not a big fan of zipper closure. I was debating between TB Cache and SFBags' sleeve. The SFBags sleeve was a bit too "nicely made" with higher price tag, especially with the optional flap that adds another $15. It's a nice sleeve and you can configure to make it as an independent bag with strap rings and piggy-back compartment for accessories. It's just that TB Cache was simpler and cheaper, exactly fitted to my needs.
All in all, I'm happy with Cache.