Matt Ahrens, one of the original ZFS authors, has somewhat recently stated that for ZFS the OpenSolaris/Illumos/FreeBSD versions are on par, but Linux and OSX are behind.

I've had issues this year w/ Ubuntu 14.04 machines where the kernel modules would not build, resulting in zpools that could not be imported. I guess that's more of a packaging issue than a code issue.

I periodically have unexpected behavior where my filesystem doesnt mount right and I have to re-mount, or the nfs exports have to be re-exported, etc. I've assumed this was due to incomplete configuration on my part but it's clearly not as brainless to set up as native fs.

Short answer for me: It hasn't been tested as much.

I know a zraid3 FreeBSD/ZFS root array will still boot with two drives failed and one drive acting wonky. Not so sure about Linux.