I love how securely Shimano QR levers close (I have the Ultegra 6800 version) but the offset lever arm is difficult to position in its fully closed position. I had the lever arm adjacent to and almost touching (rather than under) the left chain stay, but as FBinNY said that makes it really difficult to open. So when the Enve ones went on sale I upgraded; nice weight savings too.

ENVE Titanium Skewer Set [100-0012-004] at BikeTiresDirect

These internal cam QR skewers are supposed to be made by / in collaboration with Mavic. The internal cam mechanism feels the same as the QR skewers which came with my Mavic Ksyrium Elite wheels.