Ive been to the Chicago convention a few times now, and the celebs are super friendly! I was pretty terrified myself, specially when I was getting a hug from Jensen in a photo op, but it is definitely worth it!
Hehe, I know that feeling! And funnily enough I've never been to a convention but I have been to only 1 concert (Russel Howard concert if you count comedy as a concert :/, if you know him your a legend! But if you don't it doesn't matter ^^)