Pros
The Lab is known is for its strong reputation in science and research. If you are in a science-role you will have opportunity to grow and bring glory to yourself, the Lab, Dept of Energy, and USA. You will have access to leading edge technology and personnel. The Lab's vacation policy, and easy going & laid back attitude is one of the biggest reasons to work here.
Cons
If you are a non-scientist or a new scientist, you will not have the same opportunities as established research staff. They once had amazing benefits and compensation packages. But these have been whittled away by years of lean funding from the US Congress. This means they are unable to repair or refurbish buildings, roads, walkways & curbs besides actually trying to pay people a competitive salary. Don't forget about entrenched people-managers who are terrible at managing people.