Pros
I think the salaries are on the high end for reps compared to other companies. I think they are as good as or better than any pharma company when it comes to allowing you to run your business (within limits). Anyone who has been a pharma rep will understand this statement.
Kontras
Merck has lost most of it's panache. It used to be rather prestigious to be a Merck rep. It no longer is. Merck has had legal trouble, which lost them a lot of respect and trust. They have also had trouble with products in the media (negatively). They have had 3 or 4 layoffs in as many years. Management moves around a lot. The purchase of Schering Plough resulted in a big layoff in spite of employees being told most of the layoffs would come from the Schering side. The year prior to the purchase was riddled with unkept promises. Overall, it is not very safe to be a pharma rep these days, for any company. Downsizing is a way of life for them all. Merck, as well as other pharma companies, are hiring third parties to decide how the cuts will be made. There is no consideration of tenure or performance. They are cutting based on geography, and the position you hold. Do not expect loyalty for a job well done.