Can the Kinect be used as a control interface for Mac OS X? Is there software and/or drivers that support using the Kinect to replicate the same behavior triggered by the Multitouch gestures? Would it be possible for me to swipe my hand leftward in the air and switch to a different desktop or space, for example?

It would seem there's two steps to make this work. The first would be to establish Kinect-to-Mac communication. We know this is already possible by the various hacks already available.

The second component we'd need is to translate one form of USB input (the Kinect's) to be assignable to the multitouch gestures. We know this may be possible because software like BetterTouchTool allows nearly infinite customization of multitouch gestures.

So... is this possible?
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.