Pros
You will work with some top-notch technical people at the staff level, that are the best in the world at what they do, in spite of the decline at Sandia more generally.
Cons
With 8000 employees, there is much variation across the labs, but some clear and disturbing trends are in place. The top 3 includes 1. A belief that any manager can manage anything. This leads to managers who move between wildly different organizations often, which causes them to be largely ignorant of the technologies they manage, the customers’ needs for those technologies, and the skill-set of (and trust in, and loyalty to) those whom they manage. This also contributes to the next two problems. 2. A belief that any engineer can do any job. This leads to a discounting of subject matter expertise, demonstrated accomplishment, and experience. While probably exhilarating for new employees, this becomes quite frustrating after a few years. This is also evident in how scarce research funding is allocated. Of course, when a crisis appears, then the management seems to remember who the ‘go to’ staff are, but after the crisis passes it is business back to usual. 3. Because the previous problems discount individual skills, there has developed a strong preference for process compliance over technical accomplishment. Miss a training deadline for whatever reason, and wrath will rain down on you. If you never produce anything useful in your career, you can coast along to retirement, as so many do. Another outcome of this is that more value is placed on bringing in new work than on satisfying existing customers. Another outcome yet is that in hiring new staff, this leads to an obsession with metrics like GPA, and all but ignores less quantitative measures of, say, attitude and references.