I use SVK - while better than SVN,
- that's not saying much
- it still has issues
Incompatible changes still have to be merged by hand. Some CPAN modules may change a couple lines a release. Then, there's modules like DBM::Deep that will add and remove whole files and those that stay will be significantly changed, even though the API and behavior that you care about hasn't changed at all.
My criteria for good software:
- Does it work?
- Can someone else come in, make a change, and be reasonably certain no bugs were introduced?