Pros
Firaxis had a diverse set of engineers coming from different philosophical backgrounds. As a developer, this forces you to think about problems from an angle that you may have overlooked. The people at the company are excellent, both within their fields of expertise and as individuals working together. The studio has a very tight knit feel, and has maintained that feeling through a period of growth. Honest discussion is encouraged.
Cons
The compensation is low for the amount of work and domain knowledge that is required for the position. It frequently feels like there is far too much to do and not enough time to get it done. The work-life balance at the studio is good, but not as good as I had hoped it expected coming into the position.