Most medical schools in North America are 4 year programs. The first two years focus on pre-clinical, lecture based theory. The final two years are practical, hospital based training where we actually learn how to practice medicine.
Being lecture based, the first two years are very similar to undergraduate years...just a lot more work, a LOT. As an undergrad, I usually had 6 or 7 final exams per term, which is more than most undergrads because I was in engineering. In medicine, I had 10 or 11 final exams per term. On top of that, each exam had considerably more material than I ever dealt with in undergrad. So, like I said, med school is a LOT of work.
Looking back, I have definitely learned a lot in the past two years. Not just about the science of medicine, but also interacting with patients. As physicians we have a limited amount of time (often only 10 minutes) to talk to patients when they are most vulnerable. Comforting and reassuring a patient with that kind of time restriction is definitely a skill that takes time to learn and experience to perfect.
I'm interested in seeing how things progress in the next two years, when we get to put theory into practice...