My school is also on a systems-based curriculum. It's relatively new, so they're still working out some kinks, but I love it. We started with "Foundations" in the fall, which was two separate blocks, starting with biochem and genetics and ending with microbiology and immunology. We started systems in the spring, and had four blocks so far. Personally, I love that everything is integrated in one course: anatomy, physiology, pathophysiology, pathology, histology, physical exam, etc. For me, it sticks better when I can see the big picture. Nothing about med school is like undergrad or grad school; we basically had 3-4 (non-mandatory and available on podcast) lectures every morning, and then occasional mandatory sessions in the afternoons, including physical exam, interdisciplinary workshops with other health profession schools, lectures and workshops about health disparities and inequities, and patient panels where patients come to talk about their experience with chronic diseases and conditions that we learned about during that block. We also had a few really interesting sessions during systems; for example, during our cardiology block, the coordinator set up a session where we got to examine patients with known cardiac conditions and we tried to diagnose them, with a fellow in each room to guide us. Another time, we were assigned to go to the ER and take a detailed history (and physical for those of us who had learned the relevant physical exam stuff by then), and then present to the attending, who was really cool about keeping it low-pressure and all about the learning experience. And we had preceptorships with local physicians who either practice IM or pediatrics.
Our exams are generally biweekly and cover material from lectures and anything else we covered in those two weeks, whether we were focused on gross anatomy, pathology labs, or physical exam. During systems, we also had "shelf" exams (NBME subject exams) after the second block exam. We had two major exams with standardized patients, one in December that assessed our ability to take a detailed history on three different standardized patients, and one in May that required us to do a history & physical, write it up, and then do an oral presentation at the end. Second year will be essentially the same thing with a few more major systems blocks followed by a capstone, and then we have a short amount of dedicated Step 1 study time next spring. We are required to take Step 1 earlier than most other schools because M3 starts May 1. Apparently it's designed that way to give us plenty of time for electives, but I haven't learned many details about the specifics of clerkships yet, other than that upperclassmen and graduates tell me our school prepares us well for the real world.
I know it may sound crazy, but I think med school is a lot of fun. It's hard work and pretty time-consuming, but the way it's structured, we get to see the relevance of what we're learning. I volunteer in the student-run clinic, where med students (M1 through M4) work as a team to do the H&P, come up with a plan, and then present to an attending who approves or modifies our treatment plan. I'm surprised by how much patient interaction we have, and how much practice we get "playing doctor." My class is also extremely diverse, ranging in age from under 20 at the white coat ceremony (!) to 40-something, and from so many different cultural backgrounds and prior career paths. My only regret is that I don't have a little more time than I do to socialize with my class, because they're a really friendly and unique group. But I do get a lot of time with them during PBL and TBL sessions, as well as during the few club activities I do participate in.
I would say that at my school, all of the classes are potentially equally difficult, since they each cover all aspects of that system. There were some systems I enjoyed more than others because of my own interests, and I know what my strengths and weaknesses are, but nothing was particularly overwhelming. Drinking from a fire hose is definitely an apt analogy. I'm glad I had a strong background in upper-level bio courses before starting. If you get a chance after finishing your pre-reqs, it's not a bad idea to take physiology. If I had to identify one course I think helps the most, it's physiology, because it's relevant to everything in medicine, and it's one of the few key subjects that isn't memorization-based. Once you understand it, it's much more intuitive when you're using it again during med school.
I hope that answers your questions; sorry for the novel! As far as work-life balance, I think it's possible for everyone! I'm not a genius, and I think even the most brilliant people still seem to work hard to assimilate the sheer volume of information, but my day looks pretty similar to what Ecce described; I like to be done with everything by 8-9pm and relax with my husband. I usually wake up early to work out, but I'm also pregnant and if I don't get my workout in before my day started, I find every excuse to skip it at the end of the day! I attend class and try to have my work done in time to eat with my family. Honestly, there are some days I am flipping through Anki cards at the dinner table, particularly right before exams. But I usually have one weekend day completely free, or at least free enough to spend half a day doing something fun with the family. Weekends between blocks (every ~5 weeks) are also family time. And during the first two years at least, you have the flexibility to attend a school play or conference or ball game during the week. In that sense, the first half of med school is more flexible than every job I've had! It's definitely doable for parents of kids of any age, I think; it just requires the ability to adapt to different routines every so often and a great support system. There are three other moms in my class, and parents of kids of all ages (from fully grown to toddlers) in the classes above mine. The most important thing is that your family is on board, because you will need the support. My husband is my rock; he's incredibly patient and flexible and encourages me to do whatever I need to do to succeed, since it's important for my entire family. It's important that your spouse is prepared for your schedule to keep changing throughout the process, and for you both to keep communicating about the future and thinking ahead about your five-year plan and matching and all the things that other med students may not have to consider as far in advance. Any questions, feel free to ask!