I'm blown away by the depth and intelligence of all these comments. So unlike other social media.
As for personal experience: I went through two startups. The first cratered and was a horrible experience from start to finish. The other IPO'ed.
Did the first make me a better person? It would be hard to make that argument. I spent 10-15 years recovering from it. However, it made me realize that the startup is, as the cliche goes, "the lengthened shadow of one man." The folks who ran the second one are not just smarter than I am, they are better people.
The old-fashioned notions of "character" really do apply here. You can also make money in a place led by bad people, but you have to more careful because they won't hesitate to screw you.