Pros
This company gave me a chance when I was in college and was looking for business experience. It's also not the worst entry-level full-time job out of college. When the system works, and you're able to get to get the products you need in a timely manner to the customers you work so hard for, it can be a very satisfying job.
Cons
When the system doesn't work (it frequently doesn't), this job can be agonizing and stressful. Fastenal seems to push a new (and different) sales initiative every month, only to be quickly forgotten about the following month. There have been sales contests with cash prizes that I knew our branch was in the running for, only to be forgotten about by management when asked (these people are the ones who were so gun-ho when the contests were introduced). They tout the people at established stores as the models for success, but the personnel at those stores usually had nothing to do with establishing their successful customer base. Also, the word "raise" is a taboo word at Fastenal. Expect to fight for every dime, even if you are constantly getting praise heaped upon you.