I've made 6 purchases from BinTac. Some of them were keepers, others I passed on to someone else to enjoy. Bin is easy to get in touch with for any questions, parts & service. In my experience he stands behind his products -- but yes if you decide you just want to return something because you don't like it, you get a restocking fee. I have never done this... instead on a few AEAs I ended up selling, not because they sucked, but they just weren't for me, I sold them here on the marketplace for a decent price and they all sold almost immediately.
If the product is actually delivered defective they will swap or repair it no problem. And if you run into an issue and let's say you're way out of warranty, they will put you on the phone or video call with a tech to teach you how to fix it. And yes he does videos on YouTube teaching people how to do many of their own repairs, maintenance and proper operation.
So I don't know about "horror stories" with AEA -- at least with BinTac and his affiliated dealers. I think people need to do their research before they buy any product, make sure they read any fine print on returns, and also learn to perform basic maintenance on their guns. A few of their products are known to have parts that will eventually wear out and need replacement. These parts are generally cheap and available so you can keep an extra on hand. Most of their products I have found to be fairly robust (and accurate).