Pros
I genuinely love working at MA - in my 20 year career this is the only place I worked that I can say that - I think this is high praise for the company. I think the CEO is approachable and genuinely cares about his employees and tries to do right by them. The project I am on is the most difficult thing I have ever worked on and it challenges me in good ways. The people are great, its a flexible work environment, good pay, health care is expensive but I view that as the country's fault not MA's. If you work and you are a self-starter, the management will recognize it and reward it. If you see an opportunity here that interests you, you should give it a shot, I don't think you will regret it.
Cons
I don't think this is truly a con, but the health care is expensive - I see that as a function of the country/world, not necessarily MA's fault.