I don't know why anyone would make the switch unless they needed to for some reason.
If what you have still works for you why make the change or spend the money?

If I want to dabble with other operating systems I play around with the free Linux distributions.
You can get them in Linux PC magazines in bookstores, or even in libraries.
Some have Live CD's that can boot and play from the cd/dvd drive so you can get a feel for if you like it with out having to install anything.
Then if you do like it you just click the install button.
And if you have a windows product on the hard drive already it can set you up with a dual boot system.

But I suggest reading up on dual boot systems before doing it - especially if you have files on windows that you do not want to chance loosing.
I have set mine up both as a dual boot on 1 drive and now I have the Linux {mepis}on my second drive.

Some of the Linux distro's are easier to work with and some are more challenging.
The fairly easy to use and install ones that I have found are -
Mepis {or simply mepis} my fav so far
Ubuntu /Kubuntu

Linux info if interested -
http://www.linux.org/
http://www.linux.org/dist/
http://distrowatch.com/
https://www.mepis.org/
http://www.ubuntulinux.org/