I've been reading through the pre-reunion book of personal updates, and find them revealing of personalities and surprising about careers.
Some people write veiled boasting, sometimes in the Bobo style of boasting of success both in profession and obscure hobby: e.g., "I like to unwind post-call on the llama farm, just 20 minutes from the Mayo Clinic, where I'm doing my neurosurgery residency." I made up that example. David Brooks has already elaborated in great depth on this style which combines serious and ironically-wacky.
Other people are perfectly honest about difficult circumstances that people wouldn't have otherwise known about, including failing to publish during graduate school, having had an ill-fated several-year-long relationship, etc. Some find a middle ground between Pollyanna sunshine and brutal honesty, and mention issues like divorce that people might have noticed by reading the class notes over the years, or issues which are semi-difficult but of the everyday variety such as dating.
A really striking issue --- the reason I'm writing this --- is looking at what happened to people from my undergraduate major. My undergraduate major was in a right-brain field reputed for brilliance at a top-5 school. The two most brilliant people from my major got PhDs in the field from top-5 schools, but now neither is in academia nor particularly prestigious jobs. I'm shocked. I knew that the labor market in this field was challenging, which is why my PhD is in a completely different field from my undergraduate. It's shocking that people whose brilliance I saw continually for four formative years of college, who were at the top of the top of the top, did not get their first choice careers. I know at least one of them would really like an academic job.
The people who left the field for fields with fewer quantitatively smart people, or fields where other traits determine success, seem to have done the best. I exclude myself since I'm fully aware of my neuroses, and am neither on the tenure track nor at a prestigious university.