Pros
Opportunities to learn all about the various facets of the business. MKS has a relatively flat organizational structure. This encourages interaction and communication between the various functional departments. It is a welcome alternative to mega companies and their job specializations. Job security is very high with MKS. This is a good and bad thing for the company. However, it's good for employees because it is a partial result of a lack of expectations. MKS wants to keep employees in their niche within the company without moving them on. This means that once an employee gains mastery over their current responsibilities, they are secure until they want to move on. A somewhat flexible office environment is also nice. Though to be honest, it's not much better than any typical engineering company.
Kontras
It is no secret amongst employees that MKS pays on the low end of the scale. Employees typically begin their tenure in the ~25th percentile. This might seem fine except that MKS doesn't give raises based solely on performance. Therefore, if (and that's definitely a big "if") raises are available, everyone will likely get a nominal cost-of-living raise and that's about it. The employee then will never actually approach an average or above average base salary. Low employee expectations is also a negative. Though it breeds job security, it doesn't help a person retain satisfaction with their job. MKS does not expect growth, but rather competence.