It sucks because of its fanboyz. Let me give you one issue.
Some young lady ordered a computer from Dell. For whatever reason, the computer ended up being a computer with Linux instead of Windows. This lady tried using it, and ended up completely lost, unable to take her classes at college, and wants to have Windows on her computer again.
So, how to Linux users react to it? With extreme hostility. A comment calling her an "airhead" gets moderated as a positive, helpful comment on Slashdot.
Pathetic. Someone tries Linux, decides they don't like it, and wants Linux removed from their computer. Linux fanboyz react to this person by calling her every name in the book.
There's a reason that Linux is a failure on the desktop. It's not because anyone who doesn't like Linux is an idiot. It's because Linux has some serious issues that they need to resolve before Linux is ready for the desktop.
In the meantime, I will continue to use Windows XP as my primary desktop operating system, and a VMware image of Linux for development work.