Pros
Big name recogntion and the opportunity to network with peers and colleagues whom may be able to help you advance into similar fields. Also, their infrastructural support is outstanding in terms of access to information and business analytics that can help to perform job functions effectively.
Cons
With a big name comes the diminuitive status of the employee, you're just a number. In the event of a "restructuring" there is little rhyme or reason that is used to determine those that stay and those that go. Third parties are used to make the decisions in order to avoid legal trouble, thus no party can speak on your behalf to ensure you keep your position. In the sales force where "performance" is allegedly paramount, top performers are frequently let go and mediocre employees with more tenure are allowed to stay on board. Also, due to the size and reputation of the company the payscale is much more conservative than smaller pharmaceutical companies.