Paul,
Have you seen
git the distributed version control system...?
I have been using git for the past 6+ months for version control in my driver/kernel projects and for other user space app projects...
It was a little daunting at first in a
multi-developer environment (locally at work with my 15+ linux driver peers, and publically with the linux kernel community)... but I found it to be very powerful... its strengths are in its ability to do branching, merging and
rebasing (this really blows me away).
When debugging my driver, I create a new branch, I do my edits/compiles/tests/commits... then I merge this branch back into my local branch for this driver (I have separate branches for the various drivers)... then if my peers made intermediate changes, I pull their changes from their trees into mine, I rebase my changes on theirs, and now I have mine/everyone's changes... all done with a few simple command lines.
I'm sure that for a smaller developer headcount, git would be very easy/quick to learn/apply.