Pros
There are so many!
Fist and foremost is the community. There has not been a single person I couldn't tolerate working with, and the vast majority of personnel were genuinely a joy to get to interact with. I've had very positive interactions with everyone from technicians, to PM's and research engineers, to even the CFO (phenomenal guy!).
The research being performed is frequently interesting, and if it isn't you are encouraged to find some that is! The culture is one where work with other divisions is encouraged so even if your interests conflict with the work being done somewhere else at SwRI, you should be able to do it.
Cons
While the pay is not bad, it is not above average.
If you want a lot of time off, that is possible, but little of it will be PTO.
The culture and work environment can very significantly by division. Mechanical Engineering has been exceptional. I have worked with Space Sciences and with Chemistry / Chemical Engineering Divisions and have enjoyed all of the interactions with the personnel in those divisions. I have not had positive interaction with automotive, and have heard from several independent personnel that that is neither a personnel-minded nor forward thinking division.