I've just managed to convert my workplace from Team Coherence (an
obscure, locking-not-merging, revision control system to subversion :-).
It took me six months to convince my co-workers that it would be a good
idea. Git, bzr or mercurial would have taken much longer, especially
since I don't actually understand myself how the interaction between
developers on a team working towards a common release really works. At
least, not without someone blessed to produce the final source tree and
thus having to go through all patches.