I haven't pushed it very hard. I'm only using it for personal stuff.

That said, it's pretty good at DWIM for a command-line tool. It works as advertised and doesn't require any fiddling once you have it set up.

cons: command line syntax is verbose. Enough so that there's a wrapper for it (http://duply.net/) which I also recommend. Access to backups isn't as straightforward as with forest-of-hardlinks approaches.

I'd be interested to hear how it holds up to production use.

some of the comments about rdiff-backup (below) might also apply to duplicity, since it seems to share much of the same internals (duplicity seems to be the encrypted version of rdiff-backup).