So I exchanged mine for a large and had a much better experience. Overall I really like them, but there are a few issues. With the medium, it didn't fit well and wasn't possible to center on the board. The footbed didn't have nearly enough boot coverage. On the Large version, it's too big for an ideal fit. Basically if you have a size 8 foot, you're kinda screwed, but getting the Large is at least workable.
The ratchet mechanism is not the best quality. After a few hours of use, one of the toe strap ratchets no longer clicks and catches the tooth under moderate pressure (and I'm not tightening them to obscene levels).
As others have mentioned, when locked, a little more pressure can still result in it moving.
I had some issues with heel slip, and tweaked them throughout the day. The appeal is the quick entry, but in practice, I'm finding that doing them up that way is resulting in heel slippage. Sometimes it works better than others. It's nice when you kick your foot in and lock it and it feels just right, but so far my experience has been that more often than not, you'll still have to mess with it.