Pros: the excitement of working where r&d are at the top in the world!
Cons: i worked long hours as a manager, looking back now, my work-life`balance was not good.
An incredible place to work, unfortunately, in 2007, LLNL was taken over by Bechtel and was forced to lay off 400+ employees, and I was one of the managers laid off due to Bechtel bringing in their own managers.
The most difficult part of the job was leaving! There was always more to do, more to learn. The science, technology, security, etc., that was going on with the scientists' that I supported was interesting and exciting, making working there a very proud place to work.