Pros
The number of fascinating & challenging projects coupled with the level of intellect of fellow employees makes going to work a stimulating experience. Taking this job directly out of school (w/ Masters), I've had many opportunities to lead existing and start my own research projects. Initial pay is extremely competitive compared to cost of living of area. The programs for new graduates to help them establish a research foundation (e.g., attend grad school, oversee own research for 2 years), has been widely used and bringing in new talent to the Labs.
Cons
Bureaucracy within the Labs can hamper project development and external collaboration. Employee review and promotion cycles rarely offer any useful feedback to help employees better understand how to move up ladder. Combine this with a very bottom-up approach (employee-driven) to research & development choices, it's confusing to determine the direction senior managers want to take the company.