Most people here are really busy all the time, but its a mix between coursework and clubs/activities/outside projects. There is quite a bit of reading, but you learn pretty quickly how to prioritize between courses and many of us form reading/study groups to help balance the workload. I wouldn't say the work is any harder than things I did in the past, but there is a lot of it. It depends on the courses you take -- law and some security studies courses can be heavier on the reading, while business courses require preparation for case discussions.
I don't think there were any surprises -- Fletcher was really open throughout the admission process so I felt like I knew what I was walking into. I like how flexible the curriculum is and that you can take courses at any of the Harvard schools. The most different thing for me was how you register for courses -- there is a shopping day at the beginning of each semester, and you don't start to enroll until then. I had been used to enrolling in classes months ahead of time.
I'm particularly interested in technology in international policy and I hope to work in corporate tech policy or strategy - many of my fellow students are doing security studies, conflict resolution/negotiation, or international business relations.