I picked one up from a local best buy. I find it nice to use, the nub doesn't bug me to much and I'm wondering if I can get a case to work with it. I did test the powermat charger with half of a PS3 game case between my X and the receiver and it worked. How much does it affect charging? That I don't know, Powermat does say that it reduces the charge effectiveness.
My thinking would be that some cases would probably add enough bulk making the nub flush again. This is a theory, but I need a case that will accommodate that new battery door. It's probably adds 2mm in thickness which is a lot.