Pros
Management compensation sets you up well to become a solid, established adult very early on after undergrad; tuition benefits get you a degree for free; learn how to have difficult conversations, seek feedback, assess and improve operational performance, and interact with senior leadership; dated but effective warehouse management systems that may feel rigid or dated but is actually excellent; amazing individual contributors with excellent institutional knowledge to share if you are thoughtful and humble towards them
Cons
Reviews do not always feel based on merit or actual business impact. I saw some people save the business millions in direct labor costs year-over-year but not receive any better of a raise or performance eval than somebody who did not. As I've gotten exposure to other industry practices, I've seen that McMaster's are not normal. Very challenging to be promoted internally, and limited opportunities for people with English as a second language. When you go into other distribution environments that are as "elite" as McMaster, trainings are offered in multiple languages, and supervisors/managers are often fluent in Spanish and English and promoted from within. McM has a diversity problem and being more open to ESL folks with supporting structures and training would help. They also don't pay facilitators more than individual contributors and they really should. This is a standard practice in the industry that they are missing.
Perfection was the expectation for management and ICs. Feedback felt more like personal attacks than real attempts at developing my skills and abilities. Was constantly made to feel like my personality was a problem and I could not communicate. New job provides exact opposite and positive feedback on both fronts almost every day from folks with a broad variety of styles & expectations. McM wants a bit of a one-size-fits-all personality type and way of thinking, but many can be effective.
A lack of emphasis on the P&L and various cost structures really limits the business perspective that folks hired into management get. You can be very successful in leadership at McMaster-Carr with none of the financial literacy that would be expected of you at other companies.
Last, the culture amongst management is very competitive and not collaborative. A lot of gossiping and unconstructive conversation happens. Director styles differ but fall into only a few different buckets, resulting in myopic visions for the company and limited growth/cost savings. They need more diversity of thought in upper management tiers and to bring some outside expertise in at the top levels. Too many directors+ are home-grown for 20 years and they'd benefit from hiring for some roles externally.