Why Not to Use ZFS

Also the IOPS of RAIDZ is, as you said, about the same as a single disk - but only for writes. For reads, it scales fairly linearly like a RAID0.

It is definitely good that you outline all these shortcomings, since people need to know what it is bad at as well as good at. However I think you are wrong that compression and checksumming are "usually not worthwhile" - surely it depends? I've found the compression to be excellent for VM disk images (unlike deduping). And the checksumming has been invaluable in large HDD arrays built with cheap consumer-grade disks. With a large enough array, the usual CRC system can sometimes fail to detect errors.