|My Desktop at the moment|
There are obvious categories of people that this post is not meant for: Hardcore gamers (let's face it, gaming options on Linux are seriously limited), People who live on Visual Studio/Photoshop and Microsoft employees. For everyone else, there's Linux. ;)
I started using Fedora as my primary OS last year, when I got my own laptop (I have since switched to Ubuntu due to the whole 'ease of finding and installing software' (PPAs) thing). Using it on the desktop was never an option. For one, I had a USB modem (unsupported by Linux) and my mom was constantly on Excel, and retraining her to use Linux would've been a lot of work (not that difficult, but I tend to cut corners when it comes to my parents).
Anyhoo, I was never a serious gamer, nor used Office obsessively. Most of my work is done on Google Docs (or in text files. I'm using gedit to write this post) and most of the time I'm stuck on a browser (Firefox 4 there, which coincidentally is leaving the testing phase and being released today!). Banshee is much better a music player than either Windows Media Player or Songbird, and GIMP works really well if you're not really into photoshop but want to mess around with some images or something (there are a load of extensions for it that make so many things possible). Emesene is an awesome Windows Live Messenger clone, and Pidgin is the best chat client that money can't buy.
And for those pesky tasks that can only be done on Windows, I have installed Windows XP inside a Sun VM VirtualBox (but seriously, FUCK ORACLE!). I've run MS Office 2003 and SPSS 13 (a statistical package by IBM) without issue in the virtual box.
I've used Linux exclusively for over 6 months now, and save a few occasions when newly installed kernel images refused to boot (rebooting always fixed the issue), I have faced no major issues with the OS. No blue screens, no security threats, no OS crashes and little or no unstable software. This in spite of me using Alpha or Beta quality software (Hotot and Firefox).
So, my friendly advice to all of you looking for a change is: Think about it. Find out about it. Run a live CD, experience it. Discover that Linux is not all typing complex commands into the console (in fact, the themes coming out these days can pwn Windows sideways!).
Also, for the latest updates on Ubuntu and free software, check out OMG! Ubuntu! :)