Vantaggi
Because IMS has a virtual monopoly on their segment of the market, there's lots of different departments that have lots of different areas of focus, so you can find something you're interested in. They also have facilities all over the globe and lots of people work remotely, so there's some flexibility in moving around within the company (that said, most geographic locations are tied to the certain previously mentioned departments/areas of focus)
Svantaggi
Upper management is very removed from the day-to-day interests of the employees. Lots of bureaucracy and disorganization slows down even simple tasks, like expenses or requesting a new PC b/c your keyboard is literally falling apart and keys are falling off during client meetings. Management is very focused on cutting costs - usually not by improving efficiency, but by reducing pay. Salary increases, vacation time, bonuses, and promotions are all handed out sparingly & you have to fight for it. Departments are very siloed and only care about what affects them, not very much "same team" atmosphere outside of your department.