I saw this coming about 6 months ago when I started playing with ZFS. At the time, the next release of OpenSolaris was already way overdue, and I had yet to be impressed by the progress between any two releases I'd seen over the years I'd been watching the project. It was clear to me that OpenSolaris wasn't winning hearts and minds, so by the time I started my ZFS adventure, it was already out of the running as far as I was concerned.
I ended up picking FreeBSD 8, for a bunch of reasons:
Really, actually free-as-in-beer. As opposed to the "free only if you need less than 4 TB" come-on offered by Nexenta.
Really, actually free-as-in-freedom.
I learned this lesson back when transitioning from Novell (!) UnixWare to this new cool thing called Linux. I spent an unholy number of hours on Usenet arguing with the UnixWare fans, trying to convince them that Linux was going to take over the *ix world. The UnixWare fans would keep pointing out this little advantage or that; and they were right, UnixWare did have some technical advantages at the time. They saw me surfing a wave behind their serious yacht and only saw the surfboard, and didn't realize that it would take a tsunami for me to be surfing that far out. A decade later, we're still skimming the splinters of their yacht off the ocean surface.
I believe the same thing will happen to Solaris, sooner or later. I have more than just SCO in mind when I make this prediction. Think on how many other marginal Unices have already fallen and how embattled the remaining biggies — AIX and HP-UX — already are.
My only bit of unease here is that I'm not sure that FreeBSD won't also end up under the waves. It could be that Linux + btrfs will someday take the ZFS advantage away from FreeBSD. But, if it does, you still have the two freedoms to fall back on. Consider the least popular of the BSDs, NetBSD: even complete marginalization isn't enough to destroy a truly free OS.
It ran on hardware Nexenta wouldn't. This is more than just an anecdote, it's a reflection of the fact that some OSes get more driver support than others. If this is your only criterion, of course, you'd run Windows, not *ix of any sort. Since it isn't, you have to ask how far down the slope toward "truly rotten driver support" you'll allow yourself to slide. Windows > Linux > FreeBSD > Solaris, in the driver support area.