cPFence We’re planning to start fresh on ext4, it’s not worth the hassle.
I still think btrfs offers some benefits for this kind of file storage (with some limitations as well). We will stick with btrfs for now, but if we run into any issues, we will switch to ext4 (reformat the attached hard disk) for our /backups partition (now you only need to specify a mount point, not a device).
Thinking out loud: I wonder how Enhance would cope if you deleted the current /backup partition and reformatted? Really, the correct ownership and users etc should be set with the first backup sync.. I'd probably check with Enhance first if we did try this in the future.