Since they mention wall mounting, I take it that to make it thin, they had to put the buttons on top or they did away with buttons altogether, relying solely on a remote, which seems unlikely. From the looks of it- if this has buttons, they may be touch sensitive and fingerprint magnets. Keep the cleaning cloth handy.
I would think only a small percentage would wall mount as it defeats the purpose of making it thin - you suddenly have a giant black wart on your wall with wires dangling, or you are drilling holes in the wall and snaking wires around inside them. Either way, you have a thing on the wall that people will constantly ask: "WTF is that?!?!"
I am also a bit leery running a disc player at a right angle to the Earth. It seems it would make disc handling even more annoying and prone to dropping than usual.
Or, you can set it on top of something, which seems more likely and you could still access the menu buttons easily if needed.
BD-P4600 popularity prediction: Fail