Yes, my only phone is FxOS. No, it's not good enough. I'm sure if I was on better hardware, it would be okay. My only requirements for it are a) decent web browser (it fails on this point) and b) Google 2 factor auth (I'm using GAuth[0]). I really don't care about playing games on my phone (I have a hacked PS Vita for that) and I have a laptop for everything else.

[0]https://marketplace.firefox.com/app/gauth