Pros
HHMI is a company with great benefits and had an environment supportive of a work/life balance. Janelia Research Campus is a beautiful place to work and is filled with smart people who are doing interesting things, but not everyone raves about their work experience or growth opportunities. I've personally had sufficient opportunities for advancement that I've stuck around for a while, but most of that is because the managers I've worked for cared about me.
Cons
There are too many managers, and some of them seem to create obstacles for the people under them instead of removing them so they can perform to their full potential. There's a lack of trust and effective communication between and within some departments that really hinders progress on some long-term projects.