Pros
Big4 experience is a plus on your CV. There is some good people there that you can learn a lot from. Fun way to start your career if you are ready to put down the hours.
Cons
Lack of respect for lower level employees. Promotions and pay rises not linked to competence or performance. Office politics and your ability to align yourself with the right people is the only thing that will drive your career forward here. There is a significant gap between what senior management says and how strategy is implemented by the lower levels of management. By promoting based on office politics rather than ability there are some truly horrible managers / directors / partners with social skills that makes you wonder if they shouldn't really be committed to an institution.