Pros
Sandia is an employer that is generally flexible, values its employees, and serves a noble purpose in support of the nation's security. There is a great team of people at Sandia and the benefits are pretty good as well. It is probably one of the few companies that still offers a pension. Sandia also offers a robust health/wellness program which is attractive for those interested in maintaining a healthy lifestyle. It is not uncommon for people to spend their entire career at this company; often rotating into various assignments along the way. Unlike many companies in private industry, Sandia can offer a sense of stability which is attractive to many of its employees.
Cons
Beauracracy defines Sandia. The policies and procedures, while defined, are often so rigid that they prevent sensible business solutions. Gaining exception to processes is just as redundant. Sandia's culture is very risk adverse and it has deep roots in doing things "the way they have always been done". The downside to having long term employees at this company is that there also seems to be a "pay your dues" mentality, which can be frustrating for those looking to advance quickly. Also, there is a heavy focus on gaining education from top tier schools. This is the only company that I have heard of that focuses on why potential new hires got a "C" in Art History over ten years ago.