My experience with my yubikey is that it just works. I know that's not terribly useful info, but it's really all I have after several years of occasionally using it. Oh, it's been on my keychain all that time so isn't terribly flimsy.

They're good. My yubikey works flawlessly, though very few sites/apps support them.

Nitrokeys are way more advanced and FOSS, but they are still somewhat expensive.

I press my yubikey by mistake and end it just sends random messages on Slack, other than that it just works fine.

Not enough sites support them and for some reason they haven't made one that supports USB-A, USB-C, and NFC on one key. Seems like the most obvious configuration to cover everything.

I've only used Yubikey when work mandated them for a while. Didn't last long until they moved to a push-to-phone-app system instead. It was fine, just irritating to carry around one more physical thing.

And I prefer a smartphone based app in personal life. I use Authy, keeping my backup codes in several safe locations and separate from where I keep password vault backups.

There's probably some super duper FOSS alt to Authy but I haven't spent the time to look for it.

Yubikeys are rock solid. I have several bio keys that read fingerprints and I have no complaints.