To meet and learn from others who are willing to share their WordPress experience
Yes.
All of the above.
6 months and counting. I have been rapidly consuming all the WordPress knowledge I can get my hands on. The Codex is your friend.
Networking/Socialising with experienced and not so experienced WordPress users/designers/programmers.
It's a great place to learn about WordPress with people of all levels of experience both techies and content producers. Why wouldn't you want to join?