Pros
-Colleagues are incredibly talented, professional, hard working, and an all around pleasure to work with. -Management understands the importance of work/life balance. -Salary and benefits are solid. -Having "Merck" on your resume will help you throughout your career. -The day-to-day job is fun and rewarding.
Cons
Chemistry management simply does not care about discovering drugs. They treat the department like an academic institution by emphasizing visibility, publications, and external presentations above all else. First line management (Directors) are more or less ineffective. They have too many direct reports, and their seldom interaction with them leads to them being out of touch and disconnected from the lab workers. This further leads to year-end reviews that honestly look like they're just guessing. Promotions are inscrutable. Management refuses to provide any clarity to the process. Playing games and politicking helps, but your work certainly doesn't.