Pros
Expand has a very flat, flexible structure that allows the sufficiently ambitious and pro-active to rapidly get exposure to C+ level clients in Tier-1 Investment Banks, contribute meaningfully to analysis and strategy, and eventually lead projects (this is not an easy ride, but a rewarding one). The firm has often targeted exceptional job candidates who provide an element of academic rigor not present at some larger firms, while not losing sight of key business objectives, and remarkably avoiding excessive self interest / company politics. Some of the most fantastic people to work with.
Cons
Integration with BCG is taking time, and the company has yet to reap all the benefits of this association. Starting salary is very average and lower than larger consultancies, although the opportunity to increase and progress in the company is notably more competitive and meritocratic (usually after about a year's tenure, but sometimes earlier). Within 4-5 years you may be notably ahead of a counterpart in BCG.