First of all, congratulations! Secondly, just breathe and stop worrying about all of this so soon. You will fall into a routine once your classes begin, and your routine might be very different than those of your classmates or of someone from a different medical school.
But since you asked, I'll throw in my perspective.
What did your daily schedule look like?
Class from 8-noon daily. Afternoon classes two days a week, and free time the other three afternoons. I used that free time to work/volunteer, but it was fairly relaxed, overall.
What it was like being in a class full of really really smart people?
Just like high school and undergrad, there are different levels of intelligence in medical school. Some people are naturally very bright, but some will still look blankly at the lecturer and ask half a million mind-numbing questions. The difference is that, in medical school, the people who are struggling work their tails off to catch up, and often learn the material pretty well in the end.
I guess what I'm saying is that the population didn't require all that much adjusting to.
How stressful is it? Do a lot of people drop out?
That varies from person to person. There is a large amount of material - some handle that without a problem and others end up panicked or depressed at least part of the time. Regardless, it is very rare to see drop outs. The school doesn't want students to fail and struggling students are given many second chances. It isn't uncommon for a small number to have to repeat first year, but leaving medical school entirely is something I haven't seen.
