It has. They semi-recently switched from XUL to native Java, which has made it as fast (maybe faster?) compared to Chrome or Browser on Android. Definitely worth checking out again.
My only real complaint with Firefox Mobile is that it doesn't play that well with Intent filters like the one the YouTube app uses to catch http://*.youtube.com/* requests. That said, I'm not sure how to fix that without introducing the annoying per-link popup asking me if I want to use Chrome or Firefox.