I have worked as an early employee at a startup that was then successfully acquired. In my experience it was great, although I think it did not match the situation at most startups. I think there were six people when I started working for them, as a freelancer at first, and then eventually we grew to about 15 and I joined full time.

I did not get any stock, I was 100% remote (I live in Europe and the company was in the US, I never even met any of my bosses or coworkers), and I never worked long hours.

It was also early in my career. I started as a freelancer, and this was my highest paying job until then, so I gladly took it. The work was hard (low-level and high-performance stuff), but as I said, I did not have to work over 40 hours per week. I did have meetings in the late afternoon though, and sometimes in the evenings, because of my time zone.

After we got acquired, I told them that because I didn't hold any stock, I still wanted some payout, so they roughly doubled my salary. The work also became more corporate and there was less of the hard but interesting stuff. Eventually I left when the company that acquired us was itself acquired, and now I work for another established company for even more money.

TL;DR: the startup was acquired, I did not get a payout but it launched my career so I'm very happy I was involved.