This is a bummer. While there isn't a bump on the back of the controller anymore, it's still using AA batteries for some reason.
http://www.wired.com/gadgetlab/2013/05/xbox-one-photos/?viewall=true
Wired.com said:The controller still takes AA batteries, but the humplike compartment is gone. So are the screwholes.
http://www.wired.com/gadgetlab/2013/05/xbox-one-photos/?viewall=true