Pro: You get a TONNE of free help from everyone.
Con: ?
Pro: You make friends.
Con: ?
Pro: It's just a fun diversion from all of life's little hassles.
Con: ?
You don't HAVE to be given anything or pay for stuff to make it good, or worthwhile. Best I can say is that you'll only get out of it, what you want. The more you put in, the better it is for everyone.
Richard