Well, Subversion is the current choice of the Boost community. The Boost community has moved from CVS to subversion recently. This mean that we could change one day to other SCM. Subversion have as other SCM his + and his -. I will no enter in evaluation of what I don't know now.
But, the main advantage to use the Sandbox is that any member of the boost community could follow your work, particimate in the same project, help you by checking, testing, ... If each member of the Boost comunity use a different SCM, all of us will need to install all of them. This is a major drawback IMHO.
I agree, in general. Currently things are moving rapidly and I feel that using svn would break my momentum. As things slow down, as internals stabilize, and if people want to help and feel more comfortable with svn, I will either start reflecting my work to the sandbox or entirely switch to it. It just happened that Sergey guessed that I had a repo of some kind and requested access. So why not? In the meantime I frequently post to the vault and both Mercurial and Darcs make it possible to browse the repo via the web.
At the end, if your library is proposed and accepted, you should use Subversion.
Sure, that has always been my intent.
Best, Vicente
You too & good night, J-L