Most of them are so busy that they have very little time to answer questions and respond to e-mail. Of course, these are just rumours. I, myself, have never taken science courses apart from the astronomy ones, so don't take my word for it. I have been known to be wrong before. Once or twice.
Campus life is pretty good.
Everyone knows everyone else, just like high school. Those people whom you don't know by name you know by face. You'll also notice that the same group people make up most of your D-level courses. Everyone becomes so close and tight that you can argue and shout at each other during class and the prof won't mind. You get to know your profs too.