Steve Streeting (the man behind OGRE, a 3D graphics engine) has been writing about his experiments with distributed version control systems, particularly Mercurial and Git. In particular, his latest blog post contains a summary of his experiences with the two version control systems and is probably the most in-depth article I've read on the topic.
The most interesting portions of the article (and his prior posts) are the ones which talk directly about managing the OGRE source within each of the two DVCSs. OGRE is not a small project and it's very illuminating to read about what parts of a (distributed) version control system are important to a larger project, as this is stuff you may not personally experience until it's too late to change your mind.
For my own personal projects I use Subversion (TortoiseSVN is a great piece of software) and I'm not in any particular rush to switch over to a DVCS just yet. It's simple, straightforward and fits well with my workflow. For larger projects, especially ones where you're collaborating with people across the Internet, I'd give some serious thought to using a DVCS and reading about other people's experiences is extremely helpful.
[Edit: I ended up switching about a year after this post to Mercurial for my personal projects.]