I did not come to the realization until recently. I have been using computers since DOS was still mainstream back in 1990 back in my elementary schools days.
So I've been using computers for about 13-14 years, but I must say that the last year has been the best and most satisfying every. Never have I been more productive and less stressed than when I found Linux about a year ago. I never had to restart! I never had to Ctrl+Alt+Del shit, which is what i spent most of my time doing on the Win98 boxes that were common place then.
Mozilla has improved my internet experience multiple times over. It's faster than IE, pop-up blocker (I even forgot there was such a thing as pop-ups), and tabbed browsing saved on the all of the Alt+Tabs I used to have to do.
GAIM has helped my internet social life. It's so much fun to use. Tabbed IMs are a plus. Stability (AIM crashes constantly) is gr8 and i can automate whole convos and easily avoid people i don't want to talk to.
Overall, i've never enjoyed owning/using a computer so much as i have since I've discovered Open Source software. I am truly thankful to GNU and Linus Toravalds, and the entire open source community. I hope to live up to their gr8ness someday :-D