Pros
* Decision making is extremely academic and meritocratic. It's about what you know, not who you know, though politics did creep up from time to time. * Extremely small company with heaps of awesome technology. You're guaranteed to learn a lot here. * Most of the work that I did was extremely unique and very interesting. * Jane Street goes to great lengths to ensure that its staff is at least familiar with OCaml and functional programming in general. I think this is a good thing. * Culture is extremely lax. Office hierarchy exists in name only; everyone, including their "executive management" is extremely warm and approachable. Casual clothes policy is great. * The compensation is fantastic and their benefits/perks package was pretty wild. There is ALWAYS food in the office, and their gym is excellent for most of the popular training programmes out there (sports training, cardio, bodybuilding, basic powerlifting, etc).
Cons
* Resourcing problems were pretty evident. * Interview process was, in my opinion, too selective for certain roles. * No true career paths for those looking to get into management, as it doesn't exist there in the same form as it exists in other places. * Vacation policy is surprisingly light given the rest of their benefits. * Leaving for lunch seemed to be universally frowned upon. * No opportunities to work from home given the nature and structure of the business. * Lots of unproductive conversations about the smartest/most clever way of doing things, which made many meetings run unnecessarily long and introduced many "side projects" that slowed work in other, more key areas down.