Pros
Large enough to be an established company, but small enough that it still has a very entrepreneurial culture and many great qualities of a growing business. A lot of responsibility is given to analysts early on, and there are plenty of opportunities to contribute to the company in a variety of capacities. Management emphasizes a meritocratic organization throughout recruiting, and they mean it. Ideas trump experience and face time is pretty meaningless. Very fast career trajectory and the company's growth rate lends itself to moving up quickly, as most advancement seems to come from within. The culture is similarly excellent, with an employee base full of young, bright, sociable people. Out of office social events are quite popular, as are "Friday Beers," a weekly AlphaSights staple where everyone unwinds in the office over some complementary beverages.
Cons
Benefits could be slightly better, but there is room to improve your own pay based on performance.