I'm an ENTP for sure, although, like del, I am interested in highly theoretical stuff and can be pretty quiet at times. The latter is often because I just don't care to talk to the people (I mean how long can I listen to people talking about how drunk they got last night -- it really gets old fast, and then I crave a 'real' conversation, or barring that, my own thoughts. I feel guilty in those situations though because then I just watch the people like they are in a zoo or something -- yes it's horrible I know).
I'm here because I found out about this place pretty much by accident and what I read was just awesome. I was curious and fascinated, sure, but I love hanging out here too. I can relate to a lot of what is said here, but there's definitely a twist.
One thing I have noticed which amazes me: I am seeing people here who are teenagers and they are mentally so advanced in vocabulary and clarity of thought. My very unscientific observations tell me you guys must develop about 10 years ahead of everyone else or so.