Pros
Many very intelligent and motivated people around you. Cordial and polite atmosphere, slightly formal but not overly so. A wide range of things going on, many technologies in play. Prestige from working at an industry giant. You're working for an end user so there's no pressure for business development. Company is stable and always has cash for initiatives. Excellent corporate headquarters facilities.
Cons
Projects often drag on for years and seldom provide the promised benefits. Overambitious management has embarked on many simultaneous changes. Heavy use of service providers has degraded team spirit in recent years. More of a "seniority-ocracy" than a meritocracy; takes a long time to move up. Interdeparmental rivalries often make for suboptimal progress on projects.