I've worked at 10 startups since 2006, with equity or options each time. Only one time did it turn out to be worth anything at all (~6 months salary), and that one time wasn't even a successful "exit". It was more of an aquihire, and they paid out the options for everyone they didn't want, ie everyone not living in the Bay. The other nine times my options have been worth precisely zero, either I get let go or quit because the company is circling the drain, or fizzles out, or gets rid of a bunch of people to goose the numbers before a fire sale.

Stock options are a lottery ticket, and I value them roughly the same.