Well, i find the windows group of OS to be very intuitive, any app or any part of the OS is easy to find without having to read manuals. Which makes it nice to support. Also almost all companies I know use it so I can find lots of work. I dont agree with people who say that the windows OS are crashing always etc...because if you build a machine with good hardware, setup the drivers correctly and use only well programmed apps and look after the OS correctly then windows can be a happy crash free experience.
I am very happy with windows 2000 it is perfectly stable and provides many advanced administration features...finally an OS and server designed for the people who support it. (although you better do your homework and take a good backup before you think about upgrading any of your NT servers.
Regarding linux, I tried it once and although i got a kernel running first time no problem i found hardware very difficult to install and also it was crashing frequently in KDE probably because i had not configured it correctly. I think Linux has a long way to go to be a good desktop product because it is not very user friendly. But this is not to say that in the future it will develop into something very good.
On the server side things are much different. The cost savings are tremendous if you can get a good server running. Compare the cost to say NT or Netware with a 25 user license for instance and then add the cost of an intranet solution such as exchange 5.5