First I want to tell you, that this project is, what I ever wanted to have, as it replaces deprecated SDL and my own small Engine nearly completely.
I'm glad to hear that
So will there be future versions until it works?(as I saw many good projects dieing on half way to completion)
Of course, SFML is not going to die. Having users feedback helps me to improve it even faster and better.
And how stabil is the current release?
It looks quite stable, I don't remember of any major bug reported for SFML 1.1. But I can be wrong, so you'd better check the forum
(I know, I should keep a clear list of reported bugs and put it online... or just use the SF bug tracker)
Why are only some public interfaces Documented
All public interfaces should be documented, which ones exactly are you talking about ?
I know non-member functions are not documented (although they are in the tutorials), but this is only because I still haven't found the doxygen option to do it.