I've tried to use desktop bsd distributions before. Tried desktopbsd back in the day before development stopped. The graphical ports system on it seemed cool, until i realized it sucked, it needed a lot of polishing. Desktopbsd had promise until development stopped.
Then there's pcbsd. It's probably the best well known desktop bsd distro around. It's not bad, i rather liked its prepackaged binary system for grabbing and installing applications, but those tend to suffer from user contributions in uploading binaries that don't work or may have had install packaging errors that keeps something from being installed. No biggie, pcbsd can use the ports system, but had no graphical port utility...don't know if they still don't have one or not. The main reasons i stopped using bsd distributions...
1. I want something i can use, desktop bsd distros could definitely benefit from the ports system having binaries of everything along with the already existing source code for everything. I install some programs from ports either command line or graphical utility in desktopbsd, and you are given choices for what tags you compile the source with. Not exactly good for a desktop bsd distro to be doing to desktop users (however just fine for compiling from source enthusiasts). Pcbsd would benefit from maintaining there own ports repository for binaries as an addition to the pbi system that they use and could eventually phase out (the idea of a binary repository would be easier to use and manage than the existing pbi system).
2. I install some programs and they don't appear in the start menu of kde in pcbsd and desktopbsd. WTF? They have no post installation script to handle this for the user?
3. There is a linux compatibility layer for bsd's. I use mostly linux applications, on mostly linux, so i guess i'll continue to use linux which is much more mature as a desktop os (and especially since i know how to use it...i would however never fallback to windows just because i know how to use it).
4. I can learn some new cli skills for operating bsd. A lot of the commands after all are the same ones used in linux. With of course commands specific to bsd cli. No biggie. But, the kernel sort of scared me away. The freebsd kernel is an ALIEN thing to me! Learning what comprises it and how it does it's thing isn't quite in the public light so much as the linux kernel or the windows kernel (with fame for the windows kernel bsod'ing people). That's sort of my fault though, i didn't really have that much time back then to go looking through documentation as was busy with a lot of homework.
Desktop bsd's still have a ways to go in maturation. Desktop bsd's is still a new thing on the scene for alternative desktop os's too. I'm surprised with the push for users desiring linux to become a desktop os (and has happened fantastically), that desktop bsd distros didn't start at the same time or just a little bit after. Either 2006 or 2007 was when pcbsd and desktopbsd started getting in the mainstream notoriety of linux/unix news.
I have checked the other bsd's on the list provided, and i wasn't really impressed. Most of them appear to be still relatively new distros in the early stages and have a long way to go following in the footsteps of pcbsd.
At the end of the day, i'm a binary repository guy who loves a fantastic package manager like APT. Sorry, but YUM sucks, and the mandriva package manager URPMI will uninstall your whole system if it detects orphaned packages. The idea behind urpmi is awesome and admirable, but urpmi is undependable as it is buggy and not as reliable for downloading packages because it doesn't make multiple connections to provide redundancy for simply downloading one package. In other words is that i had to click retry when downloading packages in mandriva basically anytime i got something from their repositories. Yes, a good distro's crappy package manager made me switch back to debian with apt, that does have download redundancy and has a proper working orphan detection system (similar to my experience with ports, but just that ports is overwhelming for someone who doesn't compile source much).