Avantages
In short: for early career moves, i.e. people under 30, you will learn more and be exposed to more aspects of business -- the sides of business not seen by most until they are much more advanced in years -- in a shorter time than you would anywhere else. You will will learn and do more here than anywhere else in the economy. Exciting, even 'sexy' work. Broad and deep exposure to multiple client bases (financial services, Fortune 500, first tier law firms, etc). Best-in-class client service, product and service quality, and project management. Wonderful mentors in the practice of the trade.
Inconvénients
Company full of best-in-class experts in their fields, but almost zero business-minded people. Company still run as a specialist firm, not quite an international multi-hundred million dollar business. Horrible development culture for lower- to mid-level employees. Business designed to benefit upper management and clients only; lower level staff ridden very hard until they leave for competitors or in-house at clients. Not competitive compensation. Uniquely unsupportive management culture. Top-down mentality stifles innovation. Even upper management in regions and business lines completely disenfranchised by headquarters.