The main problem with linux is that it's much much harder to use than Windows. Could you really imagine sticking most first time pc users in front of any linux distro and them being able to use it well? I don't think so. Linux just makes too many easy tasks difficult. That and linux just doesn't have any media playing software as nice as windows media player.
As a side note, if you use linux there are still security holes. It's not bulletproof. It's still written by people.
I disagree. GNOME is highly professional and minimalistic: I'n not experienced with a terminal and rarely use it. If anything Ubuntu was easier to set up than Windows: all my favourite programs were preinstalled and my graphics drivers were even on the CD. In Windows, my wireless doesn't work and games have corruption and crash. I've always been a Windows user but Ubuntu was easier to learn. Media playing software "nice"? Totem (preinstalled) plays all major video and audio formats just like WMP, except it has a much smaller memory footprint and faster decoding. It even automatically fetches codecs that aren't preinstalled. Security holes: No, but it's much, much harder to get malware than Windows - you have fo work at it, entering root passwords, ignoring security alerts, disabling popup blockers and turning off spam filters. Windows is default root and built-in programs often require opt-in security. Name one successful Linux virus. I consider myself competent with Windows, and yet I have to wipe my system yearly due to slowdown and random crud.
Ubuntu. Linux for human beings.
If you are interested in trying Ubuntu or Linux in general, PM me and I will answer your questions and help you install it if you wish.