I've got one, but I don't use it because the main reason I got it (secure my Vanguard account) has a simple SMS backup, so it's no more secure than SMS... My phone also doesn't have NFC and the plug is USB-A on the Yubikey, so I can only use it on my desktop unless I carry a dongle around.
But I think things are better now at other services (and USB-C security keys exist), and I'm planning to redo a lot of my online accounts. I'm also getting a new phone soonish, so NFC will be an option. Just wondering if others find value in using them.