Pros
Extremely high caliber of consultants, demanding and challenging work, some access to high-level clients. Generally BCG pays attention to work life balance and tries to look after consultant's sanity. Pay is very good, and so are the bonuses. Benefits are excellent, healthcare coverage is superb. BCG gives you the opportunity to travel overseas and work in different offices if you like that, but does not force you to travel internationally. Generally, BCG is not very hierarchical, so partners and managers look for input from more junior consultants. Finally, BCG loves feedback, so you get it frequently and it is very much encouraged.
Cons
While BCG tries to look after your work life balance, often it does a poor job of it, and you end up working 80-100 hour weeks. In the SF office, management has done a terrible job of communicating with junior members. Staffing is extremely opaque; consultant's input is rarely taken into account; it's mostly about what the company needs and not at all about what you want or need. The day after our CEO came and talked about no layoffs, the office senior management laid off a number of junior consultants masquerading that as the "up-or-out" policy. Extremely shameful and disappointing. I've lost a great deal of respect for BCG.