I haven't used Mercurial, but I highly recommend darcs over git. The only advantage git has (which may be important to you) is it is much faster. Interactive recording on darcs is a joy to use.
darcs user interface is a joy to behold - it's far easier to get up and running than git, and easier on a day-to-day basis. However even on a one man project, I found that darcs performance problems started to bite after a few hundred check-ins (darcs unrecord being an obvious problem). IMHO this isn't a rare problem with darcs - any reasonably sized project is likely to hit this at some point. I also managed to get my darcs repositories into an unusable state several times just by pushing cherry-picked patches between them, which wasn't fun.
I miss darcs in some ways, particularly as getting running with git is a pain in the rear end. Fortunately darcs-git http://ftp.frugalware.org/pub/other/pacman-tools/pacman-tool... emulates enough of darcs user interface to sweeten the pill, and is definitely a good way to get started with git. I've also found that some of the functionality available in git but not in darcs has been very useful (even if it is typically a pain to work out how to use it).
any more info on using darcs-git? Looks like a python script that implements darcs user interface functionality on top of git without any need for darcs.
