Pros
At REI, I gained exposure to some of the best products in the outdoor recreation industry. I felt that the management truly cared about the staff. The work environment was fun and relaxed, but also extremely professional and committed to providing the best customer service in the retail industry. The paid sales, service and product training is excellent and comprehensive while being extremely fun. The discount and Pro Deal program is awesome and gives you cheap access to some of the best gear around, but you have to be careful not to spend all your earnings on it!
Cons
The opportunities for promotion were slim when I was at REI, but I was a part-time employee. When business is slow, my hours were cut quite severely, but this may be no different than any other part-time retail position. For myself, being a college student, these "Cons" are minor.