Avoid like the plague if you like legitimate science
Pros
Nice amenities, snacks, benefits, parking.
Cons
It's almost a joke to compare many Flagship companies to Theranos, but it's completely true. Majority of these companies are more concerned with projecting the image that they're visionaries. Yet, most of the startups are formed by ill-equipped failed postdocs that were given a god complex through Flagship's 3 month summer internship that introduces the Fellows to the FS ecosystem. Think people who tried to get onto 10 different papers as 6th author while doing minimal effort. What does that mean for you? If you're not catering to their god complex, they're gonna talk down to you on something they have no background in. This isn't just from personal experience, I watched this happen repeatedly to many people in several companies. So expect to be surrounded by people coming out of academia with heart palpitations wondering how on earth a company with millions of dollars could be running so dysfunctionally, but this is what it is. Long story short -- these companies are trying to get to an IPO and cash out. If you have any unpopular "rain on the parade" but necessary "this is science" comments, this will be strongly rebuked.