My rsync backup goes from the live filesystem (and then does some snapshot-like things on the other end with hard links and what not), but it's for my househould's shared network drive, so atomicity isn't super important. Mostly there's not many changes, and if there are, it's ok if it takes a couple snapshots to settle.

I didn't originally have that area as its own zfs filesystem, and it wasn't even originally on zfs, but I moved things around when setting up a new, offsite, backup system... Just haven't gotten around to redoing the old backups. I don't think I'd spend any more time on rsync based backups, given how I use things now; incremental zfs means no need to compare, which makes me have good feelings.