The problem is not LInux....
The problem is the mindset.
You slap on a copy of Ubuntu Gnome/KDE whichever, then give it to someone with very little interest in computers or very little experience, it will most likely work well. They won't know or care.
Most people's first experience of a PC is Windows, so obviously that's where the expectations start.
I am a devout OSX/Linux user, but Linux is simply not ready for the desktop and I think KDE/Gnome with Compiz is amazing when you consider that a group of part-timers are simply throwing it all together hoping to get it right, but at the moment nothing beats the slick user interface of Quartz or Aero, sadly until Linux looks like Windows and plays exactly like Windows, it will not cut it with more than small number of people.
Like any techy on any field ( plumbing, sparky, car mechanic, etc ) I am prepared to accept the limitations of Linux on the desktop, I use it 9 hours a day 5 days week, I live with it's odd foibles, I know the workarounds, average Joe Punter won't and unless there is someone in a shop or end of phone line who will take a mouthful when something fails to work, then Windows will rule. I hate it too, but them's the facts!
Load Ubuntu onto a desktop and then when little Johnny can't play the latest block-buster game or weird USB device won't play nice without some obscure driver being compiled, then you will quickly learn the curse of Redmond!