Pros
1) Every employee, besides secretaries, gets their own office 2) Mathematica has a good reputation in the field 3) The pay and benefits are probably better than average for these types of firms 4) Mathematica gets good contracts and interesting work
Cons
1) Limited professional development opportunities, especially for junior staff 2) Co-workers are competent but not self-reflective about their craft. 3) The culture is predictable (a plus to some) but bland. I've worked places with a much more interesting, dynamic, and diverse corporate culture. 4) Some staff in the human services research division lack professionalism. Personal relationships often drive business decisions and staff are treated differently based upon their personal relationships. 5) Mathematica does not hold staff, especially senior staff and project directors, accountable to expectations and policies. 6) There's a perception that the "Mathematica way" is the best way; there is a lot of pressure to conform. 7) As other reviewers have mentioned, Mathematica's commitment to diversity, especially in the human services research division, is suspect at best. I'd encourage you to read what others have said here on Glassdoor about diversity because I think they are correct.