I'm currently a premed at UNC. I'm working through the orgo sequence now, and I have taken the Human Anatomy class offered by the bio department, and here's been my experience with the departments:
Biology- I took Biol 252, Human A&P. Nothing to get worked up about. It was an OK class, kind of dry and boring, IMHO. Professor was a nice guy and taught the material well...he was just kind of boring though. But whatever, professors aren't there to entertain. I've had friends who have had bad experiences, and friends with good experiences in the bio department. In my experience, you have to be kind of a self-starter...big classes, but professors are willing to help people who ask for it.
Chemistry- What an amazing department! All the professors I've had have been so cool and been so enthusiastic about the material! And all of them just a touch nerdy, so that worked out for me. I've taken Chem 101 and 102 (with labs) and I'm currently finishing up Chem 261 (Orgo I). I entered with the intention of being a Psych/Bio double major, but my experience with Chemistry has been great (so far), so I'm thinking of switching to Psych and Chem. Be warned though, just because the professors are cool, doesn't mean the material is easy. Most premed people get "weeded out" by the chemistry department. Speaking of which, I should be studying for my organic chem final on Friday. I'll post about premed-type extracurricular offerings later.