I have a 3 tiered backup solution:
-my desktop and laptop use btrfs as their primary filesystems and take daily snapshots
-once a week the latest snapshot is copied to my server, which has a 4 disk Btrfs RAID* array (singly redundant). This is currently done using rsync, but will eventually use btrfs send once my kernel supports it (Debian user stuck on 3.2 here - any one have any idea when the feature freeze will end?)
-twice a year the server is backed up to some external hard drives
Btrfs provides integrity checks, snapshots, and faster RAID recovery times. Admittedly, it's still in development, but there haven't been any critical bugs in a stable kernel for a while AFAIK.
*I know RAID isn't backup, but what RAID is good for is minimizing the cost of a failure. Normally that refers to downtime, but in this case it's about preventing loss of the data saved since the last offline backup.