Earlier quoted context omitted.
Their major flaw is that they purposefully use shitty switches that fail, sometimes within months. This is true even with their absurdly overpriced gaming mice. I have never had a mouse whose buttons failed until I bought a logitech. Every person I know raves about them until you ask them how many they've had to buy.
Warranty will often get you a new one. I had a mouse fail about 2.5 years in and they sent a new one. OTOH, it speaks terribly of their quality; a mouse should work fine for 10-20 years, like some mice from 20 years ago.
And I say "replacements" because they all didn't last very long, until I got the memo and started buying decent stuff from brands like... logitech. And then there is the conundrum of going with something even more "premium" than a logitech, there's very little guarantee it's really gonna last. You may be paying twice as much for it but it still ends up lasting about as long.