I also won't store my backups in anything but my own S3 buckets (they are encrypted, privacy is not the issue). Is duplicity stable in your opinion? I am usually one to use alpha/beta software etc. but this is a long term need. I am a big rdiff-backup fan, this looks like a good alternative to my current strategy.

My current strategy is a little lame but works quite well: rsync daily to my home server and about once or twice a week an EC2 instance is fired up with elastic block store attachment and the home server does rdiff-backup to it.