I have gotten two counterfeit items from Amazon (that I know of, of course). In both cases, A2Z took care of the problem without fuss on my end. (One with a full refund-don't even send it back; the other with "send it back on us or keep it at half price".)
Would I prefer a genuine article assurance? In general, yes. Would I prefer that over a wide selection of products and range of delivery services? Probably not.