Pros
First and foremost, it's a meritocracy. Second, there are many paths to success. If you prefer technical work over publishing/writing papers, there are lots of engineers here, and the 'Engineer' career track goes as high as the 'Scientist' track. If you prefer work that's more academic, that's certainly encouraged too (with cash bonuses for certain publications in refereed journals). Finally, there a wide variety of projects. Our projects range from those that are very long running, more 'product-line' oriented (ie development tasks are fairly focused, there is a team of people to support you, etc), to those that are advanced R&D explorations (more freedom to choose direction, less worried about robustness of implementation in all areas and more concerned with proving a point / showing that something is possible).
Cons
Outside of Project Management / Principle Investigator training, you really have to identify your own training opportunities (classes and the like). On the other hand, given the nature of most of our projects, and because I get so much internal mentoring, I learn so much during the course of a year that I rarely feel the need for off-site training. The other thing that might be a downside for some people is that many of our projects end in a demo or proof-of-concept stage. People that need to see direct tangible results of their work (ie want to see a product ship out the door) can have a hard time. In my opinion, this is countered by the fact that you're always getting to do something new; it's hard to get pigeon-holed supporting a single product for long periods of time.