The joystick board appears the be the brains of this operation, it's packed solid with silicon and switches.

And two big ol' springs for the XY/AB buttons—probably so they're not too stiff, or too soft, but juuuust right.

Teardown Update: After some further research and a burn from the soldering iron, we learned that these springs are meant to close the capacitive sensing circuit used in the buttons.

Chips! Some of these guys look oddly familiar ...

Nordic Semiconductor nRF51822 Bluetooth Smart and 2.4 GHz proprietary SoC

Analog Devices AD7147 single-electrode capacitance sensors controller

Invensense MPU-6500 6-axis combo gyroscope and accelerometer

Analog Devices (formerly Linear Technology) LT8330 inverting converter w/ 1 A power switch