The world that developers and users live in is quite different. And a lot of people won't think of it as 'ScaryFox', but rather as 'CoolFox' which has all of these interesting and advanced-use buttons and knobs that let you see the plumbing of the web page you are using.

Developers want a lot of stuff in their face that the average user doesn't want to deal with. I can see the value of having a 'switch to development mode' button, but having something that's from-the-ground-up built for developers sounds like potentially a much nicer tool to use.

Time will tell if it's a good move on Mozilla's part, but I'm excited for the announcement.