Pros
If you're a consuktant, Bain & Company will teach you a lot, give you amazing opportunities (such as, you can basically pick any one of their 51 offices world-wide for a six-month case) and introduce you to a lot of important people. If you're not a consultant, the company will still promise you many of these great opportunities, but that's all just a lot of talk.
Cons
A very demanding schedule and pace, with employees pressure tested all the time. If you're part of "Consulting Support Services" (like me) you're just a cog in a machine. For example, consultants get "professional development" talks with their bosse every six months or so, I have my first such talk after six years on the job. Consultanst are made part of Baion's alumni network right away -- CSS staff like me will never be part of that network, even if we work here 20 years..