Pros
The expertise and resources that can be found here are unrivalled. The work is important to the national interest and regularly is at the leading edges of science and technology. This is a very stable environment, which can be both a plus and minus. It is important to go in understanding that you are joining an organization that has a unique governance, is not for profit, and is rarely going to be acclaimed for what it does. If you are motivated by doing something that matters for a competitive salary and a strong package of benefits, it is a great place. If you want the latest and greatest, flashy work scene., you might look other places first.
Cons
The work here is on government contracts that can be very complex and long range. You could work years on a project and not see it in operation. Security is a major part of every day. If you can't accept that as part of your day, this is not where you want to be. While you will be paid competitively and have a strong benefits program, there are not bonus and stock plans. This is offset by stability and a long history of successful work.