Pros
I work with some of the smartest people in my field. Roughly 70% or more of BBN's technical personnel have a Masters degree and above, and 25% of the technical personnel have PhDs. I love the collaborative work culture, and the team spirit. At BBN, you get to work / do research on what you like to work on, as long as, either you can bring in funds for the work you want to do, or find someone else in BBN who has the money to do what you want to do, and is willing to take you on. BBN's profit-share bonus policy on getting in new contracts is a good incentive.
Cons
The pressure of bringing in funds can at times get nerve racking, particularly if you are Scientist grade or above. BBN doesn't qualify for the (relatively easier) SBIR funds because BBN is too big to apply for those. BBN is not as big as defense contractors like Northrop, Lockheed or Raytheon (who now owns BBN by the way), to get big sole-source contracts from to keep a big team billable for years with a few capture-managers ensuring that the funds keep coming in. At BBN, each Scientist (or Senior Scientist, and above) is the person who is making the sales pitch to the customer (usually DARPA, and other similar agencies), AND is also the one doing the technical work. The average size of contracts are only slightly bigger than typical academic / university research grants. Because of that reason, and since BBN is supported completely on soft money, one has to constantly keep on the lookout for funds to keep the business afloat. Since the time of the Govt. sequestration and budget cuts, things have been particularly hard. One VERY annoying factor in recent years has been the constant interference of Raytheon Company into BBN's culture, and way of life and doing business; starting from using their ridiculously inefficient travel-system, the hundred different online trainings one has to take every year, international travel policies, the six-sigma certification requirement (which I have gained nothing perceivable from), to having to use three different passwords and keyfobs to log on your online account in order to check what course you still need to finish. Its ridiculous. I miss the pre-2009 BBN.