Pros
Very high employee loyalty. It is not unusual for employees to stay on throughout their careers. As company as grown through acquisitions many more positions are available for employees with an R&D focus and science backgrounds. Thermo Fisher Has two main focuses, manufacturing of a wide variety of science and technology related products, and a very large international distribution company selling it's own as well as others products. International company with lots of opportunity for growth and travel providing you have the experience and training to take on roles of that type. For those who have a scientific bent this is a good company to work for, since it is closely allied with science, technology and healthcare internationally. Benefits and salaries are in line and probably a little better than is the case in the marketplace. Bonuses and stock options at the management level.
Cons
As the company has grown, and especially since the merger between Fisher Scientific and Thermo Electron, the culture has become very bottom line focused. The old school, close knit family environment still exists but has been supplanted by the needs of a Fortune 500 environment. Staff level employees are well treated, but the higher you get in management the greater the pressure and, despite the stated goal of the company, the less work life balance. However this is by no means unique for a company of this size.