Work from home (that may not always be a perk, but it is now for writers), choice of flexible hours (7 AM - 9 AM starting), friendly, helpful people, great bosses, people very interested in their jobs, plus a lot of educational benefits, you are trained on all aspects of Merck and your job.
Cons
I cannot think of any, though sometimes work from home has its drawbacks, because the employee doesn't get all the information that an onsite employee would.