Phone plans are so complicated now that the representatives at the Costco kiosks can't understand all the features of all the plans of all the companies they represent. I've been told point blank that Costco couldn't get AT&T to do something that I was able to get the AT&T store to do easily. I don't know if AT&T doesn't offer Costco customers the same benefits through the kiosks that they offer through their stores, but I suspect that they do not.
Also, the new advertising campaign with the friendly spokesperson seems to be more than just lip service. Service was noticeably improved at the AT&T store I visited.