These are my thoughts on Amazon's warehousing and shipping plugin for Shopify. I've been using it for about a week or so. I have around 10 products on Amazon, which is fine. However, when people purchase a product on our website, the shipping cost, for a $20 to $40 product, runs about $9. That's pickpack shipping, maybe a bit over $9. Now, here's the big problem besides the fact that low-cost items are really bad to ship through this MCF program. The main issue is that on your own website, you have a variety of products. Sometimes people will buy two of one product, three of another, and four of a fourth. So you might have four different products in the shopping cart. When it's sent to Amazon, instead of picking, packing, and shipping all four in one package, they might ship the four items in four different packages. This costs you four different shipping amounts. Rather than saving on shipping like a normal pickpack shipping warehouse would do, with Amazon you can't save on shipping. They will ship it out, but they will charge you shipping for each product. It's kind of horrible. If a customer orders 10 products, Amazon could split that into four different packages and you'll pay for the four different charges on shipping. Instead of one box with all 10 products, you're now paying four different shipping charges for the one order. It's pretty crazy. If you sell one product on Shopify that's over $40 and have it in Amazon for over $40 too, then you might be okay for one product. But if people buy in bulk from you, you'll be eaten alive by the charges that come with pickpack shipping. If they split up the shipment into two or three shipments, you'll pay for two or three separate shipments. I'm learning that it's not cost-effective if you have lots of products on your website and ask Amazon to ship a bundle of stuff because they'll separate it into different packages and you'll pay way more in shipping than if you did it in-house or had one warehouse where things get shipped from. Amazon is great for selling on Amazon because people like Prime. But it's horrible to use as a warehousing source because of the many multiple packages and fees associated with them that can be generated from a single order on your website. You have to be very careful what you use MCF for. If it's a pricey product over $40 and you only sell that one item, it might be fine. But if you're selling products between $2 to $20 or have lots of products and people typically buy several at once from your website, you won't be happy because Amazon can split those shipments up and you'll face many shipping fee costs eating away your profit. Initially, I thought this would be a life-saving, game-changing tool. But after using it for a week or two, I'm realizing I'm paying way too much in fees for packages sometimes split into multiple shipments. Lastly, there are times when people purchase four different products and Amazon only fulfills one of those products. On Shopify, I still have to manually fulfill the other three. Even if you have inventory in Amazon and there's no configuration in the app or on Amazon to tell them to do all or nothing. If they only have one product in their warehouses and can only ship that one product because Amazon splits up your inventory across different warehouses, they should at least inform you if they can't fulfill the whole order so you can decide whether to cancel or proceed with partial shipment. Shopify and Amazon's warehousing solution is very limited and costly. I don't recommend it if you have lots of products or many products under $20 because the overwhelming shipping charges will eat up any profit. Anyway, I hope Amazon gets this fixed or provides a way to have a solution that makes shipping multiple products through them profitable.