To add to the meltpot...
Like some others I've used ZFS based servers for many years, starting with FreeNAS, NAS4Free, a raw OpenIndiana system, and an Omnios NappIT server. There's also a couple of WD MyBook ext4 style servers that turned out to be multifunction gems, very low power but now long in the tooth. There are drawbacks with ZFS but overall I've never lost any data despite occasional hardware failures. Oops that's tempting fate!
But most of my servers do double or triple duty and adding software, especially custom, isn't so easy on the fixed software appliances. So a few years ago I started flirting with Linux based ZFS installations on Intel hardware. I've grown to trust them and now all but one are ZFS based Linux systems.
In the main they're low end Fujitsu Xeon mini towers, mostly bought on special offer, with 16Gb RAM and 6x 4Gb WD drives in 3 mirrors, and run fairly quietly. They boot from a USB stick with the OS on the ZFS filesystem. I'm more familiar with CLI use of Linux than I am with BSD and Solaris derivatives so that's turned out to be a big plus. I know my way around Debian & derivatives so adding features is easy.
I think ZFS is a solution for more technical users, maybe a Linux OpenServer type solution for rather less technical types, and an off the shelf Synology type product for folk who just want a file server that works without needing to know how.
I didn't know about Xpenology, I must look it up, thanks for that.