Pros
I have worked at Merck for 14 years in the IT organization and have been blessed with really good direct managers throughout that time. They have always been good about providing training including class room on and off site and online. When i became a manager I was immediately required to take a five day management leadership course, for example. They have allowed me a good bit of autonomy to determine my own day-to-day as well as longer term objectives in alignment with business objectives. Plenty of structure, but plenty of flexibility within the structure
Cons
over the past 10 years, with reorganizations, mergers, and layoffs, coming nearly yearly, there's a perpetual feeling that your days are numbered. For many of the reorganizations that have led to layoffs, there's very little input from mid-level management about who or which positions are eliminated which tends to lead to good people being let go sometimes in droves, while mediocre to poor performers may still be employed.