I switched to FF 4 months ago and while the engine and dev tools are great it's simply not as polished as the competition.
The polish of developer tools has exactly zero to do with a browser's popular marketshare.
The polish of developer tools has exactly zero to do with a browser's popular marketshare.
All the people I know, who left FF, myself partly included, did so for this reason. Quite some sites did not work anymore on firefox. And the normal user does not care that this is because of vendorprefixes which are not standard. They care about that their website does not work anymore.
Keep the webdevs ... keep your users.