Shopify Marketplace Connect

I'm a couple of weeks in to using Codisto and I can report only good things. Listing on eBay and Amazon through the app is a pretty involved process with a lot of things to get your head around but the support is absolutely fantastic (i've has many, many questions for them!!).
Integration with eBay was quick and easy, being able to edit how listings appear from within the app and bulk edit is invaluable. I expect Amazon to be much the same once I get into that.
You get two weeks to trial it; set time aside... you'll need it. But ultimately I can see this being an extremely useful tool.