Thanks for this review. I've been using a YubiKey for a few months now, but it's nice to see there's an alternative - in case I ever need one. I have the YubiKey with NFC, and I've been able to use it on my Android.
One huge problem I see with *all* these keys is that many sites have "Don't ask again on this computer" checked by default (see the Google screenshot). This means that if you're using a public computer, you have to remember to uncheck the box. If you use public computers a lot - say, you're a college student who uses the library - then this means a lot of opportunities to forget to uncheck the box. But the moment you forget to uncheck the box once, you've just lost all the extra security benefits. Now someone only needs your password and nothing else (on that specific computer, of course).
I wish websites would uncheck that box by default. That way, when you use a public computer and forget to look at the box, you haven't compromised your security. On your own personal computers, you'll have to remember to check the box, but once you check it, you're good to go. So it's hardly less convenient, but far more security. It astounds me that few if any websites have realized that unchecking the "remember me" box would offer greater security without almost zero cost.