Pros
None anymore. The discount isn't worth the way they treat employees. You can get an outdoor gear discount elsewhere without putting yourself through the pain of only being valued if you sell memberships and credit cards. REI used to be a great place to work...but no more.
Cons
They have moved to a culture where tenured knowledgeable employees are being laid off to save money. If you have an opinion that isn't part of the "plan", you are terminated. If you don't sell enough memberships and credit cards, you will be terminated. Retail store employees and managers are taking the blame for the failures of senior leadership, and senior leaders continue to be over-compensated despite failures. In contrast, store employees are barely able to survive. It's gone from a great organization to one that is being completely mismanaged at the highest levels.