I do use Linux on servers and on my netbook.
Requires activities I am unwilling to engage in as a user of a system.
Less useful than competitors.
Uglier than competitors. Lack of uniformity in UIs. Large number of UIs that only a mother could love.
For servers though, I definitely use Linux!
Aside from that, though, my productivity on Ubuntu is much better than Windows. Workspaces, Gnome Do, the Rhythmbox integration, the ease of installing applications, and centralized updates make the occasional pains and "free" pricetag a great deal. But it's still not at all ready for "prime time" unless the hardware configuration has been thoroughly tested -- the computer I used was one I configured from scratch.
For the most part, I use each system equally, but would have difficulty choosing just one. My laptop is windows. Never tried apple much for varied reasons I won't go into.
I do use Arch Linux at home for a server, heaps of Linux VMs for different things and almost all of our servers are Linux, a BSD or OSX.
But my main laptop runs Windows 7, and I'm typing this on a Mac Mini. The Mac Mini is just better plugged into the TV, Windows 7 is generally the best Windows implementation I've used and is good enough for everything I want/need to do.
My laptop however, runs Ubuntu.
/shrugs