Yesterday at TechNet they pulled the wraps off and announced the public availability of these services. I think this is a pretty big deal; we're opening up the corpus of MSDN's developer documentation to clients outside of our control and I'm confident that usage scenarios we've never imagined will emerge as folks play around with these services.
Craig developed a reference implemenation of a client for these services of particular (peculiar?) interest to those of us who've dwelt in the *NIX world and still cling to the command line: msdnman. No, it's not a superhero -- it's a command line documentation engine that displays MSDN docs fetched from the Content Services. Craig has made the source code available and it provides an excellent example for those interested in writing clients which consume these services.
I've been helping out a little around the periphery of this project and have learned more about XML esoterica than I ever thought possible. Now when I'm asked about REST I'll have a more reasonable answer than "no thanks, I gave it up when my second child was born."