It's not undocumented as you've already said yourself...
The documentation is fully complete, the tutorials aren't yet. But most of the parts are every similar and if you understand the SFML 1.6 tutorials you should also understand how to use SFML 2, while keeping an eye on the documentation.
Tutorials are anyway only interesting in the beginning, once you understand the concept you'll always deal with the documentation directly.
You can also take a look at the also incomplete
FAQ, which is maintained by the community.
Thus just because some tutorials are lacking for a newer and better version, doesn't mean that the old version is still recommended. It's 3 years old and has some serious bugs. On top of that most of the community members can't help much with directly related SFML 1.6 problems, since they haven't touched it in years...