I use it exclusively, I'm quite happy with it personally. I do wish they allowed more than just a few specific extensions to work, though.

I use it with uBlock on a $250 "budget" Android phone and it's as fast as Chrome. The last time I remember Firefox being slow on Android was when I was running it on a ZTE phone running FirefoxOS.

The only bugs I find belong to websites, which I don't count against Firefox. I used to have to support IE8... if the site broke it was my responsibility, not the browser.

Also it has a non native scroll behavior that is awful and a deal breaker to me.

I use Firefox on Android with uBlock origin for blocking ads and kagi for search. This Google (albeit Android is Google) free browsing works extremely well for me.

How recently have you used it? It works great for me