Pros
Some very intelligent coworkers. Impressive scale of business. Exciting science.
Cons
Horrible office politics, too easy for underperformers to "hide" and hamstring the organization. You will spend most of your days trying to save your boss' (or boss' boss') job, looking for someone else to blame, or kissing backside at HQ. Poor-to-mediocre pay. When I left, I got a 25% pay bump despite a step down in title and move to a lower-cost geography. Stock has gone nowhere for almost 3 years. Clinical franchises not empowered to launch products rapidly in quickly evolving markets. Everything is driven by ancient, one-size-fits-all processes. Fossilized organization does not adapt to business challenges. Upper management spends too much time patting each other on the back. Completely out of touch with the boots on the ground. Adversarial relationship between HR and employees, Quest HR is there to minimize their liability, not to look out for your interests. If you are bullied or sexually/racially harassed, document everything and see an outside lawyer. Limited development opportunities, unless you have toadied up to the right person and are owed a favor.