Pros
Good place to start for new graduates. Lots of high-profile and complex projects and the opportunity to work with some noted experts in solving technical problems. Opportunities for those who show both work ethic and capability for advancement. If you're a top level executive its also a wonderful company to work for. From SEC filing there are lots of stock options issued and exercised for significant sums of money.
Cons
Top managers are accountants and non-engineer MBAs and so their internal focus is all about financial performance rather than how to position the company for future success. This leads to excessive focus on short-term execution (happy earnings calls) rather than long-term success of the business and their employees. Mid to upper level managers generally live with a significant workload of internal financial reporting - much of which can't be billed to clients. While the company is the largest in the space, they are not the leaders in directing where the industry goes. Generally risk averse to proactively investing and leading in "hot" areas and are usually reactive/laggards to trends in the marketplace. Skills and services not available in house have to be acquired, rather than organically grown. When the bottom line grows and the top line (AECOM and AECOM+URS) is flat, those bearing the brunt are the employees. Health benefits, training, professional development and business development have all been slashed. Raises, even for top performers are generally paltry. The end result has been lots of top performing folks leaving the company for better working environments.