I don't have IBS, but I do have Crohn's disease, which is worse. I win! Heh, just kidding. No one with bowel problems is a winner.
It affects my life as much as anything can. I don't go out, I missed the last 3 years of school, I can't work. So I'm basically disabled because of it. And i've had it for three years, since I was 14.