The six battery cells are glued to the case. It looks like a battery replacement will require a complete disassembly, and a new top case. Also, the display is now fused into the lid. On the brighter side, the SSD modules are plug-in.
http://www.ifixit.com/Teardown/MacBook-Pro-with-Retina-Display-Teardown/9462/1
http://www.ifixit.com/Teardown/MacBook-Pro-with-Retina-Display-Teardown/9462/1
