There have been tons of threads in the main forum here for months, & there is also an Amazon forum with tons of info. It is probably best to check there for solid info
-Most of their categories aren't set up yet, so only a limited number of products can be sold there currently.
-It's currently only Amazon.com, so you have to sell in USD, & apparently you have to use tracking to ship, according to other Canadians I have talked to - but I have not read the rules myself.
-They are semi-juried, so a lot of people were turned down even though their categories are open & they sell handmade. It hasn't been clear why some were rejected.
-Amazon has some of the best buyer protection online; they pretty much always rule with the buyer. So if you have ever had trouble with Etsy or Paypal not taking your side in a dispute, expect that even more with Amazon.
-Virtually everyone I have talked to says it is really complicated & confusing to set up, far more difficult than eBay (on the plus side, they have better support than Etsy)
-They are more expensive than here by far - 12% of each sale, PLUS a $40 a month charge starting in August 2016. In contrast, it costs me about 9% to sell here, counting both Etsy & Paypal fees.
One other thing to be aware of if you care about Google traffic - if you ever close your Amazon shop, they will keep the storefront open & it will almost always outrank any other site you use that name on, due to their great SEO. They use that to show searchers similar items to yours, so it will siphon significant traffic from your open sites. They refuse to delete your shop page there once you open a shop
Hope that helps!