By the looks of it, no. You can put it to your head the way you would a normal phone, and it'll work. It might look kinda silly though (since it's almost like putting a game console by your face), but reviews seem to indicate that the buttons won't get in the way when talking.
I really wish the Xperia Play sold better. I own one, and I would've enjoyed a new incarnation of the idea (or at least an upgraded version). But it seems to have failed as badly as the N-gage.