I love ZFS, but I'll also say that I also feel like ZFS is fairly slow. Of course, it probably doesn't help that most of my ZFS machines hold 10+TB of data, with lots of snapshots.

I don't feel like I'm going to be using btrfs anytime soon, I've given up on it. But there are days I wish I had an alternative for high reliability, snapshotting, and ideally deduplication (which usually tends to make my ZFS machines fall over).

I'd love to see HAMMER on Linux.