Longtime reader and writing as a small way of "giving back." I'm in my second year at H/S/W and thought I'd share some thoughts and insights. My background is traditional - think IB / Consulting / HF / PE.
On the whole, I've had a very rewarding experience so far, especially in terms of personal growth / professional development, and am very happy I went. That being said, there were a few nuances of the experience that I wish I had known about going in
1) The job search is still competitive
Some people assume that getting into a great business school will guarantee them their dream job (e.g., analyst at leading HF, MF PE, VC position, chief of staff at a "hot" startup). This is so far from the truth. True, many of these opportunities are AVAILABLE to you - but they're also available to all of your peers, as well as folks from other schools, as well as laterals within the industry. As a result, getting any of these jobs requires a combination of 1) hustle 2) having the "right" prior experience, and 3) doing well in interviews. I would take this even further and say that even jobs that hire lots of MBAs like consulting still require you to "put in the work"
2) Know what you want to get out of the experience going in - or at least have a hypothesis.
Business school is an incredibly busy time and it's easy to get pulled in many directions and honestly "go through the motions" without achieving your objectives. Between clubs, parties, meeting with people, trips...there's a lot. For example, one of my goals (like many "traditional" students) was to improve my interpersonal and leadership skills. As a result, I overindexed on classes / programs that touched on these and made sure to put in the work for those classes. This brings me to a related point...
3) Business school isn't a transformative experience in and of itself.
For example, if you want to improve your soft skills, going to school alone won't do it. You still need to do the work outside of class. Let me give two examples. Say that you want to be a better public speaker, for example. Taking a presentation class will help, but to REALLY impact change, you need to incorporate what you learned into your life. Maybe after your class you continue to record yourself give speeches and practice multiple times. Another example would be if you wanted to learn more about a certain industry - you better be networking / doing research out of class as well.
4) Many people aren't as "happy" in B school as they'll tell you. While B school is certainly an indulgent, consumer-type experience, parts of it are profoundly stressful. Many people feel like they don't have enough friends or that they're not connecting deeply with people. Many people have FOMO and go to parties they don't want to because everyone else is. Many people who were incredibly talented for their whole lives now find themselves to be "average" - which can lead to imposter syndrome. And what makes this challenging is a general culture that celebrates B school as "the best years of your life" and promises students 2 happy and carefree years. And this results in people who struggle feeling like they're the only ones as nobody wants to admit that things are hard. While for many students it is the best 2 years of their lives, for others, it's not - and that's OK.