After getting really interested in Mono and wanting to try out some ASP.NET on an Apache server I tried to get a LAMP stack going at my house.
I have never managed an open-source server (I started years ago with NT and IIS4 I think?), so there was a learning curve for me. But, when trying to go to a Linux forum I discovered the phrase "GUI" is somehow a 4 letter word.
I can work in the command line; I PREFER NOT TO. Microsoft will never feel the heat from Linux as long as the wall of ridicule to new users is so high and I have to run around several grad students' out of date pages in order to find the applications I want
Lack of support and documentation is in it's own a cost of entry.