Of the 100TB or so that I manage. 3/4 of this is on ZoL with the rest split between btrfs on top of mdadm raid6 and ext4 as /boot and some single drive setups.
everything else is ZFS on a pair of RAID-Z arrays. (though the next one will be Z2) As to why? / I almost don't care about, ext4 is perfectly fine and supports TRIM. The storage arrays are the important bits, I want data integrity above all else, hence ZFS.