Ventajas
It's a good place to get some experience for your resume. If you're interested in the defense industry, this is the largest contractor in the world.
Desventajas
Pay quickly falls behind the rest of the industry (if you're an entry-level hire). Management is often dishonest, at least at this site. Ethics are a joke. The best quote I got was from a functional when asked about doing something other than paperwork security tasks. His response was "we don't do that [my field of expertise] here..." I found a new job a few weeks later and submitted notice. Despite the acknowledgment, they're confused as to why I'm leaving. When I came here 2 years ago, this site (King of Prussia / Valley Forge) had over 12,000 employees on the campus. Last month it was revealed that there are about 3,500. This site is being starved to death (i.e., if you aren't in VA, CO, or CA, you don't really matter).