Is it a mutual admiration society,

Occasionally, but usually tongue in cheek, and only when you've been a very, very good boy.

a community learning experience,

Like no other.

an opportunity to brag about how much I know on certain topics,

God help anyone who tries to brag on this site! Your knowledge will speak for itself.

a forum to exercise my debating skills

Absolutely, and from entirely unexpected directions.

or just a nice friendly place to be?

... just about sums ET up.

"The future is already here -- it's just not very evenly distributed" William Gibson