I purchased 2 yubikey devices in May I purchased 2 yubikey devices in May, paid for express delivery, and still waiting for the devices to arrive at mine. I have tried to contact them via tweeter and emails but no headway so far

Their product didn't work Their product didn't work. Customer service offered a partial refund (excluding shipping costs). That's unheard of. When a product is returned, all payments are refunded and some will even send the client a free shipping label. When a product is faulty, that's goes without saying.

Order never shipped. Company unresponsive. Ordered end of October. Almost January and no shipment. No response from company at ALL. No stock on Amazon. Either they're having serious supply issues, or they're just a non-existent company taking money for no services.

Non Existent Customer Service - Also Just Plain Rude Shockingly bad, full-friction customer journey. Customer Service is non-existent for all practical purposes including initial purchase. I wanted to spend 15 minutes buying these security keys - I'm at the end of day 2 now and still haven't made the freaking purchase due to non-existent help from Yubico and their so-called resellers in the UK. The resellers don't actually sell anything, they refer you on to someone else. If you want to get a freaking headache then please go ahead and start your journey with these unhelpful, rude, time-wasting, arrogant people.

Solid 2FA I have been using the YubiKey for over 2 years now and it has saved me and my company from potential damage on multiple occasions. Just make sure to never lose your key ;)