A recruiter friend who normally works with startups have always advised me to treat stock options as a bonus and never a true consideration.

As an entrepreneur who's looking to build a team, I completely understand that they will try to sell you on their vision and all the benefits and wonderful things you get for being part of a startup. But you'll have to ask yourself if you feel that the vision is something you believe in as well? What stage is the startup at the moment? What's the founders' exit strategy? What is their philosophy on engineering/corporate culture?