Pros
General Managers can make a decent living if they have a large branch (over 100K month). Those aren't nearly as common on the west coast where Fastenal hasn't been around for as long. GMs can run the branch as they see fit without a day-to-day DM looking over your shoulder. You will get training to know industrial/commercial products.
Cons
Pay is not good if you are not a General Manager. GMs are expected to work 50-70 hours per week, weekend, before and after hours, whatever the customers need. High sales goals expectations. Fastenal is known for being the highest price in any market which can hinder sales. Fastenal has EXTREMELY HIGH TURNOVER. It is the #1 complaint from customers that they have a new salesperson every year. You will be fired very quickly if you don't meet the set goals and your superiors will forget what you did last month (even if you had a great month). A very "what have you done for me lately" attitude. Corporate is too disconnected with branches.