I'm been an active Objectivist for the last two years and I've met dozens of others. They're a diverse bunch (I know Objectivist actors, Objectivist musicians, Objectivist academics, Objectivist finance guys, tons of Objectivist programmers), but in general, I'd say they're way more friendly, less cynical and more optimistic than the majority of people I meet. They're fun to be around and are usually working towards some personally meaningful life goals.
I do think that teenagers probably shouldn't read Atlas Shrugged -- they're too likely to take away a shallow understanding of the message. I first read it just before my 25th birthday, and I think it's best read in your mid-20s, when your youthful idealism starts crashing into practical reality.