Why switch?
There are lots of articles that look at the pros and cons of switching. Most of those reasons are based around ideologies and seem to have little to do with actually using Linux to actually do things. Here I hope to simply address some of the benefits of switching to Linux for a writer.
A writer's needs
A word processor
While it is possible to use MS Word in Linux it is not easy to set up. Fortunately there are some good alternatives. One of them is Open Office which is a full featured office suite. It is also available for OS X and Windows so you can try it before making the switch. It will do everything you need a word processor to do - formatting text, reading and saving Word documents and spell checking.
There are also text editors and an word processor called Abiword which can be installed later.
Inspiration
Ubuntu comes with Firefox so you can still browse the internet doing that all-important research. You can also listen to music and watch videos, as well as set your background image and change the way the system looks to suit whatever you want. In fact that last one can sometimes be a bit of a distraction as you learn how to change and tweak your computer to get it looking exactly how you want it for maximum writing productivity. But at least it means you won't get bored looking at the same screen over and over. And if you do get bored then you can try a completely diffferent look for your desktop by changing to a different one.
Ubuntu does not come capable of playing MP3s as soon as you have installed it but, with the new version known as Feisty Fawn, it is very simple to get it running. Just click on Add/Remove in the applications menu, make sure that it is showing all available applications and type in Restricted. Install the program that comes up and you should be up and running with MP3 for that important musical inspiration while you are writing. It also includes Flash but not Real Player. You can find instructions for Real Player on Ubuntu Guide.
Reliability and Security
Ubuntu is a lot more secure. There are a lot of reasons for this but basically viruses designed for Windows cannot hurt your computer once you're up and running with Ubuntu. The only reason you might want to install a virus checker is to make sure you are not infecting your Windows using friends.
Ease of use
Installation and use is now a lot easier than it ever has been. Sure, it is probably a good idea to have a friend who understands linux to help you out when you have a problem. It's also probably a good idea to get a book so you understand more about how it works (Ubuntu for Non-Geeks is a great one). There's also a lot of help available on the internet.
But: If you can use Windows you can use Ubuntu. Really.
A low price
Did I say low? I meant free.
Next: How do I switch?