Pros
There are great people and a great culture in general. Able to work with top client teams on the most pressing client issues. The overall way they treat employees is extremely fair and you get the sense that they actually care about your career development. I have met some of my best friends at Bain, because the quality of people is so high, and they are almost all very interesting, fun, social people. This definitely adds to the work environment and is a big selling point for Bain. Also, it's worldwide reach allows it to offer transfers to employees who want to work in other offices.
Cons
Work-life balance can be tough at times. As with any professional services firm, you are at the mercy of your clients, and when they want something on a short deadline, you have to hunker down and get it down in a short amount of time. There is also the question of not feeling ownership of your work, since you usually only work on it for a few months and then it is passed on to the client who may or may not actually implement it. but this is true with all consulting firms, not just Bain. Overall, there are few downsides vs other firms.