Pros
Top notch technical engineers and scientists who are extremely smart and hard-working. High percentage of MS and PhD degrees from top universities. There is a great deal of freedom and flexibility if you are able to generate projects and bring in new business. There is an opportunity to advance rapidly (promotions and compensation) for the most successful who both generate new business and maintain high billable hours and personal utilization/personal revenue.
Kontras
High pressure and large time committments across all levels of the company. Ability and expertise in managing people among upper management is highly variable (some are fantastic and others are marginal). Most are self-taught with some professional development. Noticed an increasing trend toward "up and out" over the last few years. Also see more tendency for even highly capable new staff to leave after 2-3 years.