Pros
401K Matching, good benefits package, competitive salary, flexible hours, and a company car. As with any sales job there s a certain ammount of day to day atonomy where as long as you are making your sales objectives, you can take some personal time during the day for an errand and no one is likely to give you much flak. You also get to use a company car which is worth atleast $10k annually in terms of expenses that don't come out of your own pocket. Unlike many sales jobs the base salary you get from Merck is the bulk of your pay which means month in and month out your pay check is consistent, any bonuses which are typically can range beteen 1/4-1/2 of what you earn in base pay (base pay is not a function of the calculation) are just icing on the cake.
Cons
The industry as a whole is not healthy due to FDA regulation, a lack of new product approval, and merging of companies. Not a lot of loyalty from the company towards individual employees, you are simply a number regardless of how much you may have given to the company. The job gets some what tedious as it is essentially the same routine on a bi-weekly rotation. After a while you certainly aren't charging out the front door for another "exciting" day it work.