I started using firefox back in march of last year. It has gotten way better. There are few annoying bugs I found(like this, https://www.youtube.com/watch?v=mywhU2zu87c). I have not been able to replicate them consistently, So they are pending on bugzilla.

There are also some cases when websites like thepiratebay.org refuse to open, At first, I thought this might be some Mitm or DNS based block set by the ISP but then chrome opens it just fine, Don't know what happened there.. :/

There are also some lazy developers like the one at Mashape who most likely don't test their website on Firefox because if they did, They'd know there Login/Signup system is broken on firefox for the last 7 months!

Ignoring few third party related issues, It's pretty good and I use it on both Android, Linux and windows.