The only reason to use Firefox is because many of its extensions are not possible in any other browser. Watch the market share drop after the extensions are dumbed down to Chrome level.
I use Firefox because it's way faster, more stable, and from an organization that I trust. I run Nightly, which means that I made the shift to Webextensions last week. My only extension that didn't have a WE version or alternative was LastPass. No surprise, since they seem to take such poor care of their extensions anyway. That's a Deal Breaker for me, so I switched to pass.
The only addon I use is LastPass. They support the new extension format just fine. I'm looking forward to the architectural changes coming in Servo, etc, which WebExtensions help make possible. I can't be the only user like me.
I'm confident Firefox will outstrip Chrome in these areas in the next year or so. But if it doesn't... it will die a slow death and the people on HN will assure us it was because NoScript didn't work anymore.