Pros
If you can write a research proposal that gets funded, you can work on it and hire people to help you. Bringing in new business and successfully completing research projects will predictably result in promotion-- it worked for me. This organization is about as close to a meritocracy as I have ever experienced (this statement includes academia). The diversity of early-stage research is inspiring and the staff are, with only a few exceptions, first-rate. Even though I don't work there anymore, I remain on excellent terms with former co-workers at PSI and returned to do some consulting work. For what it's worth, PSI was pivotal in transitioning my career from physics to electrical engineering as a result of the research opportunities I had while working there. Unlike my at my current company, gender bias is a non-issue at PSI. Although there is a dearth of women in senior technical roles (alas, the status quo at tech companies), it is not for lack of awareness of the issue by management or because the work environment is hostile to women. However, don't expect special treatment as a woman or a minority-- a true meritocracy is just that-- a level playing field. In short, PSI is what you make of it. It is definitely possible to spend your entire career there, although I chose not to.
Cons
Technology transfer from government-funded SBIR contracts to actual commercial products is not PSI's strong suit. Observations (did not apply to me personally): 1) Academic pedigree is perhaps weighted a bit too heavily in the hiring process. 2) Opportunities for advancement without a Ph.D. in science & engineering are somewhat limited.