What’s the difference between it and Chrome or it and then regular version of Firefox? There’s a bunch of stuff for FIrefox OS devs but since I haven’t worked on anything for that platform, all I can really say is that it looks like they’re useful features. The things that just out at me as a front-end developer is the Dev Edition are it’s light, so it loads up nice and fast, something I can’t say for the other versions of the browsers I use. Although that might be partly my fault considering the add ons I’ve installed over the years. The built in developer tools, especially the console, have become just as good as Chrome’s, at least in my opinion. They’re quick and light, which when you’re working to debug something makes life a lot less frustrating. My workflow usually involves me reloading a lot and having to sit and wait gets old pretty quickly.
But has really jumped out at me is one thing. In the inspector next to some DOM elements you’ll see a little grey box with the letter “ev” in it. Click on it and get this:
It’s a small difference but really all the browsers are so close now that it comes down to a matter of personal preference when pick which one you’ll use regularly. Give Firefox Dev Edition a show. I find the best way to figure out if something is actually useful or not is to use if for a week minimum. I did that and now I think Firefox Developer Edition will be my go to development browser for a long while.