People who worked at startups, how was it? Do you recommend it?

Don't do it. Can wholeheartedly say fuck startups, especially if you're not an expert in your field.

YMMV but they've been an extreme version of the horrible crap that goes on in corpos; ex layoffs because why keep your senior devs when someone newer is much cheaper and the company only has a few millions untill next round of funding.