Can the Kinect be used as a control interface for Mac OS X?
Possible? Yes. Available? Not yet. There have been plenty of reports of people using the Kinect with OSX but no one as of yet has release any definitive software package that allows for gestures to be used. Most people don't seem to be releasing their software.

Check out this video:

http://www.kinecteducation.com/blog/2011/04/20/kinect-controls-mac-os-x/

It's the closest thing I've seen to what you are asking.

EDIT:

There is a step by step guide to getting the Kinect to connect with the Mac here:

http://kinecthacks.net/connecting-kinect-to-mac-os-x/

So if you wanted to mess with it yourself, that would be the place to start.