You should basically be able to do everything in linux you do in windows, if you are willing to learn how to use the different applications.
There are linux equivalences for most windows applications.
I switched because I was tired of pirating software for windows in order to do what I wanted.
I like to experiment with random things and all the best apps for windows seem to cost money.
I didn't want to buy a piece of software just to screw around with it and stealing it left a bad taste in my mouth.
Every piece of software I've wanted to use in linux is completely free, that is what I like best about it.
Also, if Vista is any indication of future Microsoft OSs, then I couldn't go back to Windows even if I wanted to, because I can't
work with Vista at all. Plus, I don't have to worry about viruses or spyware anymore (not yet anyway).
Also, the level of control you have over your system once you become experienced in linux is worth the time it takes to learn it IMO.