I've never thought of my introverted personality as an obstacle to overcome with regard to acting. Theatre's my reason for existing. [That, and learning... everything... but I digress] I find it fairly easy to imagine being someone else, and slipping into their perspectives/behaviors.
I am extremely reserved for the most part, so it comes as a surprise to most people when I express my passion for acting. I'm not the person on stage anymore. Not quite sure a lot of people understand that idea. Just really losing yourself in what you're doing. Losing a lot of outside awareness. Kind of.. well.. like when you're enamoured with someone, "love at first sight," and you're in a crowded room, everyone else around that person just sort of melts away, and everything that anyone else is saying just regresses into those monotone noises all the adults make on the Peanuts cartoons. And fades out.
I can say, though, "improv exercises" generally make me uncomfortable. However if there's a need to improvise in a scene from the current production, I'm fairly flexible. I guess I feel like I have something more to work off of, and I know the objectives, so I can still carry on toward those. I definitely would like to improve my general improvisation skills, though. Maybe I just don't like practicing with others unless it's an actual rehearsal of the play/musical we're working on. Little unrelated improv exercises aren't fun for me to participate in, though they are fun to watch. Maybe I'm just very neurotic...
Anywho. There's my tuppence.