Come and join us in two weeks at the second EU OpenZFS summit in Paris
http://www.meetup.com/OpenZFS-Europe/events/218873174/
http://www.meetup.com/OpenZFS-Europe/events/220183795/
And you will see some OpenZFS core devs and people/companies active on the topic.
Illumos distro :
http://www.open-zfs.org/wiki/Distributions#illumos
OmniOS and SmartOS are pretty active...
https://github.com/omniti-labs/illumos-omnios/tree/master/usr/src/uts/common/fs/zfs
https://github.com/joyent/smartos-live
And ZoL is on the ramp up, my team is pushing a contrib BTW and in case it may be of interest to you guys ? :
https://github.com/Alyseo/zfs/tree/json-0.6.4