Their search is pretty terrible. Everything else (the ordering process, delivery options, delivery time, returns system, etc.) is pretty fantastic. From my phone, I can order, say, another batch of my favourite kitchen towel brand in about 5 seconds. It will be in my hallway the next day. I don't know of anyone else that does that.
Amazon is scary in that way, because the ease of which you can magically manifest goods through its app means it becomes ingrained your routine, even to the point where you're itching to order something, even if you don't need it. They've really nailed the worst of consumerist culture, too.
It's also scary in the sense that they're slowly becoming the source of everything I buy. Whether I want household stuff, electronics, a suitcase, some hardware tool -- I invariably reach for Amazon unless it's something I know that Amazon doesn't have. (Amazon is still pretty useless for high-end, quality home decor and furniture, for example.)
As for the search, I suspect it works fine from Amazon's point of view. It's designed to offer you products that Amazon thinks you will buy, not what you searched for, and it tries very hard not to return "no results found". It is very frustrating for "power users", though.