As an SCM practitioner for the last 20+ years I've seen/worked with a number of version control tools, both commercial and open source. My personal preference is Subversion over (in order), CVS, PVCS, Perforce, Clearcase, Harvest, Dimensions. I never tried Mercurial but I've hear a lot of SCM'rs saying good things. You'll notice that Git didn't even make the list.
I've recently joined a company using Git and as an SCM'r have always prided myself on being able to provide a simple, consistent work-model for basic version control work (checkout, commit, tag, etc.). Git is such a different animal that even a 'simple' process is difficult to get to. For the 'social' coders (ie; freeware coders who like to see what somone (anyone) else is doing, GitHub is a great 'lounge'.
From our developers perspective, they hate it. They spend hours figuring out how to do the simplest of version control actions. Literally, one of our developers entered the scrum one day, said he was going to do 'xyz today', the next day he said, 'I'm going to the xyz that I said I'd do yesterday but spent 8 hrs wrestling with GitHub'
From a SCM'rs perspective, I'm less than impressed and Git lengthens my day in a negative way. Be very wary of this tool. Simple, SCM-centric efforts are no longer simple, nor can they be trusted. A case in point:
[ul]* Try to find the branch a tag has been applied to.... outside of using the gitk interface? I'm sure there is a command string that would do this but I haven't found it yet.
* Hook scripts which are central to managing the repository are severely limited in being able to control/monitor commits as not each commit has to enter the repository in the same way. Repositories can be distributed to local filesystems, then commits can be wiped out of the history with a 'rebase' so the history going into the repository is different than the original commit.[/ul]
So, the better, freeware tool you're looking for? Subversion Hands Down!
Also a good barometer of any tool is if it has any history like a forum here on CM Crossroads. You can look at the forum history to see what the pitfalls are and the expertise is available when needed. You'll notice GitHub hasn't made the list here yet either.