I’ve recently looked at monotone.
Monotone is a very cool version control system. It is still too young
to be used for real, but it is definitely a big step in a direction I
like.

It is really different from the “standard” tools we’re all used to —
the ones that work like RCS, or CVS, or their various analogs. For
instance, in monotone there is no central server. In fact, one need
not have one anywhere.

It seems to solve all the problems I have with CVS, including the ones
that subversion doesn’t address (and won’t, as I understand it, in
1.0). Monotone is always distributed. Branches and forks are cheap.
There is no distinction — and this is very cool — between positively
reviewing a patch and committing it. I.E., with monotone you can read
a patch, reply to it (with a cryptographic signature), and it is
immediately accepted into everyone’s tree.