I don't
Here's why:
Stability/reliability
Sorry, but windows still doesn't cut it. It's gotten alot better, but still not good enough. Particularly when you're working on clusters of remote machines a continent away. But then, Windows has lousy remote access anyway.
speed
Ok, it's been a few years, but awhile back I benched some of my code on NT vs. Linux on the same box. NT got smoked.
remote access/
Windows still doesn't have decent remote access. I'm regularly logged in to 3 to 5 machines in 3 different timezones, on 4 different OS (SGI, Sun, FreeBSD, Linux). It's as good as being there.
ease of use
Sorry, but navigating a tree of menus with a mouse isn't ease of use. I don't want to drag & drop to move files, or click a menu in a seperate application to reorder a file list. Opening a seperate application just to find a value in a directory tree full of files?? How can you live without grep at your fingertips Learn some sed, and you don't even have to open an editor!
If I have to reach for the mouse to do these sorts of trivial things, it's cumbersome.
And multiple desktops ... I can't believe MS hasn't grabbed that idea yet. That's one of the most painful things when I have to work on a Windows box ... being contrained to one desktop.
source
I've customized, modified or fixed several apps that I regularly work with.
I've also suggested improvements to apps that got incorporated in days.
freedom/control
I own my OS. I control my computer & my data. I don't have to agree to a license that says somebody else is allowed to remotely alter my system without my knowledge. My data isn't bound up in proprietary, undocumented, unsupported-in-the-next-version file formats. I don't have to ask nicely for a new license if I move my disk to a new computer. I'm not beholden to the MS continuous upgrade cycle.
ethics
Microsoft plays alot of dirty pool. Frankly, I feel better about myself not supporting it.