The kinect has been used by teams for the past few years. In 2012, Microsoft actually gave each team a kinect in the kit of parts. I'm not sure if it was used before that, but I wouldn't be surprised.
Here is a short tutorial on our website:
http://ratchetrockers1706.org/vision-setup/
We used the O-Droid X2 last year, and are using the O-Droid XU with the asus xtion (it is much lighter).
The kinect is actually a really good piece of hardware. Many research groups have been using it because of how good is it and how cheap you can get them now, which I believe is in the ballpark of $50 used at a local gamestop.
I'm not sure how it will fair with the pi, but I'm sure it will work out fine.
Here is a nice paper describing the math of solving for camera pose estimation I referenced in the academic paper I wrote about the 2012 vision program:
http://publications.asl.ethz.ch/files/kneip11novel.pdf