I've never had a negative experience with them. At some point everyone will get a bad product from any manufacture. So if I get a single product from Anker and it has issues. It doesn't surprise me. If it fails within their warranty period I know they will take care of it. I follow their policy and only buy from Anker.com, Amazon (Anker Direct,) and other authorized dealers.
There are a ton of happy customers out there. You can find happy customers on the various review sites, reviews on Amazon (Anker doesn't pay give away free products for reviews on Amazon), and on the community here.
Those that have issues with Anker, usually get a hold of a fake product, a product purchased from a 3rd party and has to deal directly with them, those buying from an unauthorized dealer, the product was damaged caused by the user, or the product is out of warranty. These types of issues aren't covered by warranty and customers get upset.
Anker for the most part will take care of their customers.