The problem I have with Linux systems is that I'm not a computer person.
See, I am an extremely computer savvy person (I have my masters degree...) and I still don't get along with linux.
On office systems its fine and for people who only ever browse the internet or make text documents its wonderful.
I would never recommend anyone to run it on their personal PC though for the same reason I dispise OSX. Games.
Anyone with even a passing interest in games or a desire to play anything bigger than an in browser one needs to be running windows. Sure there are tools out there for running certain games on linux/osx and even some that are written with them in mind but it really doesn't compare.
I know a whole lot of people who live and die by linux for their personal computers but I get the impression that most of them do it because they want to sound like they know what they are talking about or just to be different. Windows is a perfectly capable operating system for basically everyone (thus the popularity).
In conclusion:
If I was building a server or an office workstation- Linux
Personal computers- Windows
Personal computers for elitists who don't know what they are talking about- OSX
[/rant]
Sorry. That was completely tangential to the original point but I really hate it so much when people start recommending linux to the people as a cure all when in reality it requires a certain amount of expertise to even use it without breaking it.