Not sure if this is saying anything, but I use Mercurial for a pet project. I initially used CVS and then Subversion but didn't like the central repo design very much. When I wanted to put some other small things in there, I had to move them to the hierarchy instead of just initializing a new repo wherever I currently was. It was only a few commands, but even they were too much of a hassle for me. It just felt too heavy-weight for my purposes.

I don't remember how I came to DVCSs but I made myself a sketchy and very subjective overview of the most popular ones.

• Darcs seemed innovative and awesome but had some fundamental design flaws that made me wary of using it, even though I probably would have never hit the resulting bugs (afaik, they will be addressed with version 2.0.0 which has gone into testing recently. Might try it again then). Also, I didn't find the documentation/tutorials that good.
• Git's interface just seemed too complicated to me. Too many commands, too many things to keep in mind. I hear its CVS/Subversion gateway is top-notch though. Documentation is now extensive, but... hum. I don't know.
• Monotone had a strange database thingy to store stuff. And the manual was overly verbose to explain the workflow. Turned me off somehow.
• Mercurial looked simple and powerful. Its readable hands-on tutorials finally sold me (e.g. made it clear to me that branching is nothing more than copying a repo to a new place for independant development and then merging changes back later. Darcs' documentation left me confused on this point).
• Bazaar looked inferior to Mercurial for whatever reason, so I avoided it :P

I don't do much programming anymore but still like Mercurial. I guess that it doesn't matter what you use for small projects, since the above DCVSs will do just fine. Just use whatever appeals to you most.