Back in November, I described darcs as perfect for my needs. After using it for a while, I'm switching again. Darcs is very cool, and has a real advantage over traditional source code control systems (it's completely decentralized). But for my one-person projects, I don't need that decentralization, and darcs has disadvantages as well: it isn't as mature or as widely adopted as other tools, and it sometimes gets very slow.
Also, I can't get out of the sequence-of-revisions mindset. So now I'm trying Subversion, the "compelling replacement for CVS".