Personally, though I'm not a committer to Gambit Scheme, I am extremely leery of revision control systems other than the two tried and true open source ones, cvs and subversion, and of those two, I prefer subversion as a user. All of the others either have some hidden gotcha or are lightly used. For example:
Darcs -- hidden gotcha is that it's written in Haskell git -- lightly used, only exists because of the Linux kernel mercurial -- lightly used
Moreover, most of the IDEs and other development tools interface to cvs and subversion. So unless you've got some *hard* requirement that subversion can not meet, I'd recommend subversion.