Pros
Salary and benefits are above-average at McMaster-Carr, regardless of your position. The company quickly gives inexperienced hires fresh out of school the opportunity to manage people. As a member of the management team, you don't have to work killer hours if you can get your work done efficiently. If you are looking for a place to just put in time and get paid well, McMaster-Carr is a good fit.
Cons
McMaster-Carr is not a place where you can develop many transferable skills, so beware staying too long unless you want to remain there forever. Innovative thinking and challenging projects are in short supply for supervisors and managers because senior leadership places enormous value on guarding the status quo against progress. They are far more likely to hold an hour-long, multi-department meeting about what salutation to use in emails than about what strategies are best for growing the business and defending against competitors. The ambition and intelligence of senior leadership remains to be seen, which is disheartening for all of the people below them. I sat near the CEO in several meetings and often wondered if he was awake.