I noticed there's a checkbox for "make FirefoxDeveloperEdition my default browser," is that just a vestigial thing from the regular FF installer, or is it actually safe for me to use FFDE as my regular browser?
This page says "We'll include experimental tools that aren't yet ready to ride the trains to release." But https://hacks.mozilla.org/2014/11/mozilla-introduces-the-fir... says "It’s a stable developer browser which is not only a powerful authoring tool but also robust enough for everyday browsing." So maybe the browser part is stable, but the tools are experimental? And it uses a different profile by default, so a br…
So the browser itself should be pretty stable, but the devtools may not be.
It may also gets developer-specific UI customisations which never get merged into the beta/release channels.