Pros
It's easy to shine and be a standout employee given the quality of your peers (Although what that says about the overall quality of CTS employees is not flattering). However, the ability to shine doesn't matter, since promotions are not based on performance, but rather are apples to oranges tiering among 70K+ employees.
Cons
Limited career options. Pigeon-holed into accounts/technologies. Corporate support is the ABSOLUTE worst in the industry (HR, Finance, etc.). Lots of work with offshore (translation: hand-holding and all-night calls) and general incompetence/inability to be flexible to meet client expectations. CTS sells itself to clients as a company that has transparent teams, but clients only stay happy due to on-site manager's ability to buffer stakeholders from the true day-to-day chaos that defines Cognizant.