Firefox with U2F?

Does anybody here regularly use Firefox with FIDO/U2F for two-factor
authentication?  Does it work reliably for you?

Because it doesn't for me.  Sometimes it works, sometimes it doesn't,
seemingly at random, and sometimes for a whole stretch of time.  By
"it doesn't work" I mean that Firefox displays its popup, but the
U2F token doesn't flash, so it isn't being accessed.

Importantly, I use ssh with U2F-backed keys a double-digit number
of times each day, and that works 100% reliably.  This rules out
various failure modes such as device permissions or USB problems.

-- 
Christian "naddy" Weisgerber                          naddy@mips.inka.de