I was introduced to the concept of collaborative development workflow with Subversion. It was a night mare for me. Extremely confusing and difficult to understand for a beginner. Wouldn't recommend it to the newbies.
I have used mercurial and found it to be pretty user friendly and fully featured.
I would use it if I had a choice in the matter and bitbucket's popularity was anywhere close to Github. But given the humongous popularity of Git (and Github), every employer and open source project I have worked for has been using Git exclusively.
At the end of the day I am glad I live in a world where there is a popular majority choice in the industry which does not suck.
I used:
Ben Buchanan (200ok)
I make some bits of the web.
SVN - ok. Was the first time we'd used check-in-only source control and it really blew peoples minds ;)
Mercurial - ok. Wasn't the worst way to transition from SVN to Git.
TFS - horrible. Don't go there.
Git - best option so far.