I've rarely had an issue with anything I bought on Amazon, and when I did, they resolved in really quickly. My only negatives are that not everything is available via Prime, and Amazon is definitely NOT always the most economical option... but you pay for the convenience of having things delivered to your door, I guess.
My other issue is with selling books on Amazon. I've done this for several years with little problems, but recently, I listed a pair of books that were brand new, but had been at a bookstore for a long time and never sold. The ISBN showed the publishing date, and I stated the year of publication in the listing details. Both books dealt with professional photography, and the contents were still valid. The buyer got all bent out of shape about the fact that books were older (although they were brand spanking new) and complained to Amazon... who found in his favor. He got his money back, and was to return the books to me, but he never did that, and Amazon did nothing about it. Seems they're like eBay, and all about the buyers, but want to do nothing for sellers.