Some problems with duplicity off the top of my head -- I'm sure there are others (there always are):
1. Duplicity uses GnuPG. GnuPG has a long history of security flaws, up to and including arbitrary code execution. Yes, these specific bugs have been fixed; but the poor history doesn't inspire much confidence.
2. Duplicity uses librsync, which follows rsync's lead by making rather dubious use of hashes. In his thesis, Tridge touts the fact that 'a failed transfer is equivalent to "cracking" MD4' as a reason to trust rsync; but now that we know how weak MD4 is, it's possible to create files which rsync -- and thus Duplicity -- will never manage to back up properly.
3. When you try to restore a backup, the storage system you're using can give you your most recent backup... or it can decide to give you any previous backup you stored. Duplicity won't notice.
4. If you try to use the --sign-key option without also using the --encrypt-key option, duplicity will silently ignore --sign-key, leaving your archives unsigned. Based on comments in the duplicity source code, this seems to be intentional... but this doesn't seem to be documented anywhere, and it seems to me that this is an incredibly dumb thing to do.
1. Duplicity uses GnuPG. GnuPG has a long history of security flaws, up to and including arbitrary code execution. Yes, these specific bugs have been fixed; but the poor history doesn't inspire much confidence.
2. Duplicity uses librsync, which follows rsync's lead by making rather dubious use of hashes. In his thesis, Tridge touts the fact that 'a failed transfer is equivalent to "cracking" MD4' as a reason to trust rsync; but now that we know how weak MD4 is, it's possible to create files which rsync -- and thus Duplicity -- will never manage to back up properly.
3. When you try to restore a backup, the storage system you're using can give you your most recent backup... or it can decide to give you any previous backup you stored. Duplicity won't notice.
4. If you try to use the --sign-key option without also using the --encrypt-key option, duplicity will silently ignore --sign-key, leaving your archives unsigned. Based on comments in the duplicity source code, this seems to be intentional... but this doesn't seem to be documented anywhere, and it seems to me that this is an incredibly dumb thing to do.