Pros
A small organization right now with great team members, both in competence and attitude. Atmosphere at office is relaxed yet disciplined. The core members are really hard-working people, and have set an example for others to follow. Very interesting algorithmic and technical problems to work on. Employees are encouraged to continuously learn and try out new techniques. Sharing what you've learned with even senior members is welcome and appreciated. Strictly five-days-a-week working (all Saturdays and Sundays off). Management team goes to great lengths to ensure that employees feel secure, comfortable and productive. Zero office politics. Considering the field this organization is working in (which has a very high entry barrier) and the skill and dedication of its present employees, it has the potential to reach amazing heights in a few years.
Cons
Difficult to find a con. Fifteen paid leaves a year, which may seem a bit less to some people. Office timing is 14:30 to 23:00 which has its own advantages (less traffic during commuting) and disadvantages (you may have to give up your evening social life).