I've used rdiff-backup daily for years, but recently needed to store backups on machines I don't control, so I gave duplicity[1] a try. It encrypts, doesn't need to be installed on the target host and is simple to use if you're already familiar with rdiff-backup and gpg. Test restores were simple, but were all first generation, so not really a good test (but there are hints you'll want to prune backups to one month's worth). I haven't figured out an acceptable way to automate it, so I've been running it manually on an infrequent basis while I evaluate it. Give it a look, if you haven't already.