I experimented a bit with btrfs some months ago as part of my parttime job at my university. The departments file server had disk failures after a power glitch, so I decided to rebuild it and add in a UPS. I'm running Debian jessie on the system, which is just a small 2U SuperMicro rack case with 12 3 TB SATA drives and 16 GB ECC RAM. ZFSonLinux needs a fairly recent kernel, otherwise I'd probably have gone with stable.
I was initially pretty impressed with btrfs, but before the UPS arrived there was another power glitch (which is fairly unusual in these parts of the world; northern Europe) and it completely trashed btrfs. I was unable to mount, scrub or do anything productive to the FS. Absolutely no luck doing anything.
After that I've switched to ZFS. I'm really happy with ZFS, even though ZFS on Linux still has some bugs. For some reason zfs threads sometimes crash when doing zfs send | zfs receive, something I've noticed a few times. Performance is pretty good. For reference I'm using raidz3. My offline, off-site backup is done on a clone of the server (OS only) and uses zfs send and receive to transfer the ZFS snapshots which are done nightly.