Pros
Genentech pays well and offers a compelling benefits package. Opportunities for lateral movement are many and thus it is possible to acquire many new skills and experiences. The campus environment is casual, but intense. It's like you're living in a different world sometimes, but they do make a good effort to keep things relatively comfortable.
Cons
As they continue to grow larger, the focus on processes is increasing. I fear they tend to lean towards least common denominator thinking at times. That is, that opportunities for advancement are sometimes dumbed down to the point where you need to have a certain number of checkboxes completed before being considered for movement. Also, the entrepreneurial spirit is dying as employees become task masters to senior management. 6 years ago there was more flying by the seat of the pants and opportunities to jump in and really rise to the occasion, but increasingly it feels like you're grinding away at the same old job, putting in more hours working at things you already know and not really getting a chance to try new things within the scope of your current job and shine. Employee roles are becoming increasingly defined and thus general skills are giving way to specialization. It is the natural evolution of big companies, but Genentech used to feel like the underdog and had a fighting spirit. That's begun to ebb now.