I have been buying from REI retail locations for years. Being able to see and try on what I'm buying when it comes to hiking gear is a big plus. On the other hand, when fit's not an issue, REI has one of the best e-commerce sites out there. When going backpacking, I find it so much easier to order all my food online and then pick it up from the store without having to deal with the hassle of shopping.
In addition, the Outlet section and their new "Deal of the Day" are a great way to save a ton of cash. Just a head's up - no rewards points for Outlet purchases and the return policy is a little different, but worth the trade off.