Pros
Technical problems are challenging and interesting. Colleagues are very smart people and the atmosphere is culturally rich. Salary and benefits are above the norm.
Cons
Technical management is quite young and with a notable exception they all started their career at Optiver; as a consequence they believe there is no other way to solve technical problems than "the single Optiver way" and cannot even consider that there are different problems which require different solutions. There's a bit of a herd approach in designing systems and applications, and straying from the path is frowned upon even when the advantages of doing so are clear or might be worth a shot. These issues are lately being exacerbated by narrowed diversity in technical recruitment, populating the engineering ranks with clones of the team leads.