Pros
You'll work with some of the smartest, most interesting & kindest colleagues you could ever have on a growing scientific issue & digitizing a new field. People here are innovative, aren't afraid of tough issues and support each other cross-functionally to make sure their coworkers and clients can succeed. The start-up perks are good and their offerings are true to their word with free lunch, 401k match, health care covered, unlimited PTO etc. Fast-paced company suited for self starter mindsets.
Cons
Like most Silicon Valley start-ups, there are scaling and focus issues. Many tasks are more manual than they should be, leading to long weekly hours (expect 50+ in the entry roles, more if you're senior or in certain departments) of sometimes repetitive work and high expectation of performance, with most of the highest achievers having almost no Work/Life balance. Focus shifts constantly, making the last mountain of tasks you completed almost useless within a quarter. There is not much room for individual career development unless you take it entirely into your own hands or stick around long enough to become a favorite.