ZFS boot support is huge. Now you can build big fileservers on commodity hardware without having to worry about Solaris or OpenSolaris driver availability.
Because I'm concerned about the future of OpenSolaris, I downloaded 8.1 and attempted to get a ZFS boot install going -- I was unsuccessful. The process is extremely complex, and the best doc you're going to get is a wiki page with incomplete and complex instructions:
ZFS boot support didn't really have a bearing on scaling up large FreeBSD storage servers. It is standard practice for various reasons to have a seperate RAID (or SSD) for booting large fileservers.
OpenSolaris had so many restrictions on the boot ZFS pool (could only be a single disk or RAID1 mirrored) anyway.
It is ironic also that you mention driver availability, when driver support is one of the problems with FreeBSD. Commercial support has been quietly but steadily eroding for the last few years. If you try to put together a big FreeBSD system, as I have done, you start to run into trouble once you leave the lower levels of consumer-grade hardware.
If you want a viable alternative to OpenSolaris, look at Nexenta. They have recently hired some of the people who left Sun when Oracle took over.
I spent some time earlier fiddling with FreeBSD 8.1 RC and was really blown away by how much more advanced ZFS is compared to every other filesystem I've ever used. It's feature rich and it's very intuitive to use and configure. You don't need to be running a massive pool of disks to benefit from the features of ZFS, either. I was just using it on my desktop and transparent, filesystem-level compression and date deduplication are really cool.
And then there's ports, of course, which is awesome, especially if you prefer to build your software from source.
I'd probably move off of Linux as my desktop OS if I could use Mangler on FreeBSD.
I'm a huge FreeBSD fan and run it on all my servers. I've tried many times to use it as my main desktop/laptop system, but it keeps falling short in those few damn nice-but-proprietary things like Skype and Flash.
Data deduplication is not available in the current version of ZFS in FreeBSD. Work is ongoing to port version 24 from upstream which will offer this feature.
Something that has surprised me in the free unix world is the ongoing strong support and emphasis on sendmail. I notice openbsd highlights updates in its releases also.
I don't know much about MTAs. From what I read, sendmail has a bad reputation for being complicated and unwieldy. I've played around with it a little and found it cryptic. But mail systems seem to be inherently complicated, so maybe sendmail attracts a lot of criticism that could is in fact only slightly less true of all programs of that sort.
What's the thinking about ongoing strong support for sendmail?
Aside from the license issue, it also helps that the guy who maintains Sendmail in the FreeBSD sources is Gregory Neil Shapiro, vice president and CTO of Sendmail Inc.
With the future of OpenSolaris being as uncertain as it is, I see FreeBSD as the potential rescue. I've been a user of (Open)Solaris, FreeBSD for many years and they are simply rock stable. FreeBSD just needs better Java support and I'd host all my Java EE stuff on it.
This was my first time with FreeBSD, it wasn't that hard. I downloaded the amd64 boot iso and run it on a VM. I choose minimal and started to extract the source on /. Pretty cool. Still extracting though :)
Is testing too unstable/rolling for your tastes? If you don't care about stability, try unstable ('bleeding edge' packages, supposed to be fine for desktops)
Seems like zfs is still unstable, at least if you take a look at mailing lists - people still reports crashes and problems. There are more hype than stability.. ^_^
It has the purpose of hosting my local SAN, Samba server, irssi sessions, and various other tools. It has sane configuration, and a wonderful package system.
While it seems your comment is flamebait, it is true that many of the proprietary hardware appliance platforms I've run across are FreeBSD. Surprisingly, I'm seeing more and more Linux in said devices too.
(Responding to your comment, not the troll grandparent): I'd agree. It wouldn't surprise me if the largest financial benefactor of the various BSD's work was NetApp.