I don't think this move is in Amazon's best interests long term. Their competitive edge with Prime is that I go to them first because I assume they'll have what I want, at a fair price and the highest level of convenience. If they are no longer the "Everything Store" then they won't be where I go to for everything...
I had a long held belief that Amazon is a principled and trust worthy company... sadly that vision is crumbling before my eyes.
They crushed all the technical bookstores because they didn't have to pay sales tax. Their customer service beyond cheap refunds is abysmal. They understand how hard it is to distinguish between stuff that is only serviced through them, but choose not to fix it. And Bezos is famous for being both an asshole and micromanager.
One-stop? Sure. Efficient? Maybe. Trustworthy? Pardon me for laughing.