I've been using linux as my sole operating system since '95, and I could never go back to windows. There are some drawbacks however:
--Steeper learning curve
--Some websites are only tested on windows and mac machines -- they ignore the existing web standards -- and don't work properly in linux. This problem seems to be getting smaller and smaller.
--Inconsistent user interfaces (although is improving rapidly)
On the bright side, it's stable, secure, free, developing rapidly, and likely to get more and more important with time.
If you want to play around with it, I suggest trying out a bootable distribution (pop the cd in, linux boots without installing on your hard drive) like knoppix.
A good place to start is
www.distrowatch.com, which tracks all the versions of linux, with links to reviews and download pages.
However, if you just want a stable, sensible OS that "just works", Macs are probably the way to go, if you can pay the price premium.