I'm using Waterfox on desktop at the moment, but I really wish Mozilla would get their act back together and make all the forks unnecessary. I'm not saying they need to die: I only hope one day they aren't needed anymore.
Also, I'm afraid that's not sustainable in the long run. How long before Mozilla makes a change so big to introduce some nasty feature that it becomes impossible for forks to stay up to date with upstream? Do they really have the resources necessary to maintain an actual fork and not just a customized version?
Of all the forks I think Waterfox is the one with the strongest case that they can continue on even if they have to fully decouple from Mozilla Firefox.