I considered switching a while back, but it only got compelling when I took the leap and switched on Android and my various desktops.
Sync'ing is great, general use is pretty good.
I keep Chrome in backup for a handful of sites that just don't work on Firefox.
Not sure if it has changed recently but for ages the regular version of Firefox on Android lacked several things that were in Firefox Nightly (eg pull down to refresh, which might seem trivial but it's annoying as anything when it's not there!)
Sync'ing is great, general use is pretty good. I keep Chrome in backup for a handful of sites that just don't work on Firefox.
Not sure if it has changed recently but for ages the regular version of Firefox on Android lacked several things that were in Firefox Nightly (eg pull down to refresh, which might seem trivial but it's annoying as anything when it's not there!)