Medium sized company, fast decision making, CEO being a MIT professor is certainly an advantage when it comes to creating company culture -- very focused and not afraid to take risks.
Ideas are valued but execution more so. Great perks -- free breakfast, dinner, snacks, company transportation. The company does serious work, but doesn't take itself so seriously --- fun loving and collaborative culture. Great leadership.
Cons
It takes some time initially to settle to the fast moving culture and decision making, but once you do, you'd enjoy the flow of work and collaboration.