ZFS development continues; they recently released encryption support. Based on the rumors, it sounds like Apple is now writing their own filesystem.

Too bad. I wonder why they did not throw support after btrfs if there were licensing issues with zfs.

From Apple's perspective, Btrfs has worse licensing than ZFS.

ZFS is more appropriate for servers; I suspect we'll see some developments in the filesystem area later this year as Mac OS X 10.7 "Lion" gets closer to shipping.

ZFS is wonderful for workstations. It keeps redundant copies of blocks and has parity functionality to keep you from having silent corruption and allowing a bad drive to sneak up on you. Running a consulting business I see many hundreds of computers yearly come in with just this problem alone for hard drive failure and ZFS would make everyone's lives so much happier just on workstations alone.