1. They do not support MacBooks if ExamSoft decides to take a crap on you during an exam- They will not give you a paper exam or a loner, you'll fail. With that being said, it's proceed at your own risk. Many people use Macs, I've never seen any one have issues. I bought a PC for piece of mind.
2. 5 questions per lecture hour, vary in size by the amount of lectures per exam, as state earlier in this thread. Usually 8-10 lectures (chapters) per exam. All computer based.
3. This is completely subjective and depends on your own personal likes/weaknesses. I hate certain topics in physiology (which made them difficult), loved all of Biochem (made it easy for me). Depends on you.
4. Much faster paced then undergrad. I used to pre-read chapters in the book before O-Chem or Biochem. We go through 4 chapters in 1 day, 20 chapters a week. Reading goes right out the window.
Best.