[Nelson69]

btrfs has the features and it's destined or ordained to be a mainline mainstream Linux filesystem (trust me on this, if you're doing serious work, you want to be on main street) but there are some cases which aren't terribly uncommon where it has some performance problems.

Hard to say if it's better than some sort of linux with zfs Frankenstein system. Would love for Oracle to make ZFS more linux friendly though, seems like a win for everybody and there are tons of users that would love for it to happen.

I don't know if I'd call Reiserfs "maintained" and I couldn't recommend it to anyone. If it is maintained seriously, my recommendation would be to rename it.