> FirefoxDeveloperEdition (which iirc is basically equivalent to Firefox Beta)

The Developer Edition replaced Aurora, which was the alpha release, one version between the beta and Nightly.

AKA: the alpha :)

Credit to them though, Aurora was surprisingly stable for most of its lifetime, despite not even being a beta.

Even more impressive, the Nightly versions of both Chrome and Firefox are (almost always) stable enough for daily use. I use them as my everyday browsers at work, and they probably crash / have bugs about 1 day out of every 2 months.

Agreed. I started using Nightly — instead of my usually Beta¹ — for the up-to-date GTK+ 3.2x compatibility, but I like some of the pre-release features, and it almost never crashes on me

1: On Ubuntu you can use their Firefox Beta PPA² as long as you don't mind that it replaces release-version Firefox.

2: https://launchpad.net/~mozillateam/+archive/ubuntu/firefox-n...

I started using Nightly for kicks and giggle around 6 months ago and my about:crashes shows me only 6 crashes (none of which were able to kill anything more than a tab (and in all the cases, the offending website was YouTube)).

Nightly is amazingly good even if it is built from the HEAD of the trunk (branch in git terms).