John Goerzen recently compared a bunch of distributed source-code-management systems in Whose Distributed VCS Is The Most Distributed? His comparison includes all of the major contenders except for SVK and monotone. He ends up favoring Darcs, which I also prefer and use to manage my projects’ code. If you’re looking for a quick overview of distributed SCM options, check out John’s comparison.
Also check out Bryce “Zooko” Wilcox-O’Hearn’s Quick Reference Guide to Free Software Decentralized Revision Control Systems, which is updated regularly. (He also likes Darcs.)
Update: fixed small typo.