Performance wasn't robust, especially on dead disks and rebuilds, but also on pools with many (>100) filesystems or snapshots. Performance would often degrade heavily and unpredictably on such occasions. We didn't loose data more often than with other systems.

"play" comes from my distinct impression that the most vocal ZFS proponents are hobbyists and admins herding their pet servers (as opposed to cattle). ZFS comes at low/no cost nowadays and is easy to use, therefore ideal in this world.