If you want to use the Developer Edition, but would prefer to use the 'Australis' theme used in Firefox and Firefox Beta, you can switch to the normal Firefox theme: just open the "Customize" panel, click "Themes", and select the theme labeled "Default":
Alternatively, type "about:addons" into the URL bar, select "Appearance", and switch themes from there.
If you want all the pre-Beta features in Firefox Developer Edition, but don't want any of the other changes, you can revert to something just like the old Firefox Aurora. This will also restore your pre-upgrade profile and session data. It's a 2-step process, and you must follow the steps in this order:
- Open the Developer Edition's Preferences page, and uncheck "Allow Firefox Developer Edition and Firefox to run at the same time". You will be prompted to restart the browser.
- After restarting, you can revert the developer edition theme as described in "Reverting the Developer Edition theme" above.