A lady who ran a music shop told me - "Keith, you're a better listener than a talker ... you'll need to speak up or [they] will never let you get a word in edge-wise". Not sure if that makes me an introvert.
If I feel particularly agreved, then I'm not shy about speaking my mind though.
I don't enjoy being jostled about in large crowds (e.g. the Folsom street fair).