I've used ZFS for 4 years and really enjoyed it. It was simple to setup and send/recv was very useful for making backups of the data on a separate machine on the network. I now have been using btrfs as I switched to OpenSuse and frankly it also just works and its been easier to setup as I didn't need to do module installs etc. However I've had to switch to rsync for my backups but that wasn't hard. The other good thing I've used is the fact I can grow the raid and can rebalance the disks this isn't possible on ZFS.