I run multiple monitors and multiple drives in my desktop, and generally one of those two things will lead me to pain when it comes to installation, or an upgrade cycle with the OS. I really don't like playing with my desktop for a half a day to get it running again when I'm trying to get work done.
Given, it's a lot better today than in years past, I just haven't had it in me to go to Linux for a month, only to have an update break something that will take hours to fix. That just doesn't happen as much in OSX or Windows.
I kind of wish one desktop platform would come to true prominence in Linux, and I care less about which one, as any one... then that one can get a lot better. I don't even mind gnome 3 or unity so much. I just want something that will keep working right through a few upgrade cycles... opposed to where I really consider not running updates on my desktop.
My last attempt at Linux for a primary OS was about a year and a half ago. I tend to get the bug to try it out every couple years. Eventually, I hit a wall a week or few weeks in that I just don't have time/patience to deal with.
PC-BSD was also a really nice option, but the limited VM options and support for current hardware really killed that for me. I think BSD fits my mindset better, but Linux has become more ubiquitous.
Either way, I would love to see a truly great desktop Linux platform for me. A power user and programmer who likes to tinker with stuff, but wants something that has an ok ui, that gets regular updates without issue. Most of the time, when I did update, it was more for something I wanted to play with other than the main OS.
Also PC-BSD is working on a BSD-specific desktop called Lumina. It's at an early stage of development so not yet clear how well it will compete with established DEs.
It will be interesting to see how far Linux goes with Wayland, said to be a replacement for X. If X becomes deprecated on Linux, probably BSDs won't travel that path and stick with X, which means X development will be more or less up to the BSD projects. Just my speculation about these things.
What I'm waiting for most is completion of FreeBSD UEFI support, including Secure Boot. Once that's available it should make dual-booting FreeBSD+Windows much easier--a great option to have.
It will be cool to see what happens in the next couple years though.