Pros
If you are looking for a great life balance, are too ambitious to work in academia (low pay), but are not that ambitious to work 70 hour weeks in the private sector, this is the place to be. The work environment is really nice and the people are really bright, even though you're bound to encounter some weird scientist types who won't even say hello to you when you cross paths with them in the hallway. It's not a crazy competitive environment so people tend to be nice to each other overall. The pay is very decent, and the benefits are great. 6 weeks of paid vacation/ sick leave + major holidays and paid emergency days. Also a very prestigious place to work. 30 Nobel Laureates have worked at RAND at some point in their career.
Cons
The internal labor market: You have to find work within the company even after you are hired, which can be stressful at times. However, if you happen to do research in an area where there is a lot of demand, then you won't face that many problems in coverage. Not that many opportunities for advancement: There are only three levels: associate, full and senior. Most people reach senior status after 7- 10 years with the company. If you are very ambitious and really looking for a place where you really want to advance in your career, then you'd rather work for a for-profit consulting company like McKinsey or Bain& Co. (but then be ready to put in the extra hours to advance there) Overall the positives definitely outweigh the negatives for certain people.