Pros
There are a few reasons above all others to work for REI. This is not a typical retail job. The quality and reputation of the company lend itself to a loyal and exceedingly friendly clientele, a substantial portion of which are in fact part owners. Beyond a respectable and respectful client base, REI puts significant resources into their hiring and training processes so that only the best of the many candidates are selected. As a result, you typically get to work with a group of over-qualified, fun, interesting, and open-minded people. Those people who don't fit into such a culture often don't last long.
Cons
A down side of the hands off corporate management of store culture is that cultures vary greatly among stores, depending chiefly on the leadership capacities of the store manager (whose judgement corporate is largely in deference to). Again, compensation is not great. You will make about the average wage for your position in your area, and periodic cost of living raises. Where I worked, that meant that the unqualified high schoolers across the parking lot at Dicks Sporting Goods were making more to star than I had after 4 years worth of raises from REI. Typically the raises are between 3% and 5% a year.