If you look at my comment history you will see that as big Xerox PARC and ETHZ fan, I am not a big supporter of UNIX in general.

Last time I touched Solaris in production was in 2002.

Yeah I did play with the OpenSolaris and Solaris 10/11 images, but really didn't saw any value on actually using it.

The fact is that *BSD and GNU/Linux variants killed the commercial UNIXes in the server room, the variants being sold are mostly tied to maintenance contracts.

Even Sun wouldn't be able to keep their Solaris business going afloat for much long.

How much businesses do bother to actually buy new hardware to run Aix or HP-UX on it?

Sun had a chance with OpenSolaris and they blew it with terrible community management. The fact that they wanted OpenSolaris to be Solaris Next with minimum to no changes posed a serious conflict with community contributions. If they had followed the Fedora/RHEL strategy things would have been different but there always that mistrust of external contributions (e.g. nobody outside Sun/Oracle could build the thing properly, let alone the binary blobs issue).

We had hundreds of OpenSolaris servers and nobody could say that in 2008-2010 they weren't the best we had for a NAS server. Linux and BSD didn't come close to having anything resembling SMF/ZFS/etc... nowadays it's a different story, I'd pick FreeBSD any day for a NAS appliance.

Over illumos?

I haven't followed Illumos lately. At the time we evaluated it and its community and it didn't seem worth it (keep in mind we were deeply depressed about anything Solaris). Maybe it's thriving today? I wouldn't know. I started using FreeBSD around 2000-2001 and so there's a personal bias there too.

From what I've heard, illumos has quite a strong community now. The events surrounding OpenSolaris caused an exodus from Oracle, and everyone landed either in illumos or in FreeBSD.

These days development of ZFS is done as OpenZFS with members of FreeBSD, illumos and ZoL. DTrace development mostly happens in illumos.

All of the above comes from second-hand experience based on what I've heard from the folks at Joyent (now part of Samsung) such as bcantrill. I have only played with FreeBSD and illumos and read through some of the code.