The Kinect is a depth camera. Nothing new there. PrimeSense had one that was a lot cheaper than existing ones, and Microsoft bought it. It was primarily the cost of the device that had PS in the running.

The skeletal tracking was totally Microsoft's stuff; in fact, it was an utter surprise to PrimeSense when it was announced (that was fun -- they had no idea what we were really doing with the camera until very late in the game).

So: PrimeSense: Depth camera.

Microsoft: EVERYTHING else (from the firmware and the drivers on up, including a /bunch/ of manufacturability stuff that PS had little experience in).