I found this bug on November 9 using Windows 7 54 bit and Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0 Turning off the preference for allowing DevEd along with Firefox, the DevEd restarted as a normal build, still DevEd according to Help>About but with the normal UI, not the dark one and lacking the Developer options included. STR: 1. Download DevEd from ftp://ftp.mozilla.org/pub/firefox/nightly/latest-mozilla-aurora/ 2. Notice it installed correctly with a new Developer Edition profile. 3. Turn off the preference for allowing DevEd along with Firefox. 4. Notice it restarts as a normal build, still DevEd according to Help>About but with the normal Austalis UI, not the dark one and lacking the Developer options. included. Actual result: Turning off the preference for allowing DevEd along with Firefox, the DevEd restarts as a normal build, still DevEd according to Help>About but with the normal UI, not the dark one and lacking the Developer options included. Expected result: Turning off the preference for allowing DevEd along with Firefox should restart the same DevEd with the dark UI and the Developer options included. NOTE: Starting the DevEd doubleclicking it's icon in the Desktop opens the latter, even having chosen the DevEd profile created when I installed this version for the first time and without the option to allow DevEd along with Firefox. To be able to get the actual DevEd (dark UI with developer options), I had to reinstall it. The First run tour didn't show up anytime.

That's what the checkbox is supposed to do: let you use your regular profile (which almost certainly doesn't include the dark theme and other modified preferences). See also the doc about reverting the Developer Edition customizations: https://developer.mozilla.org/Firefox/Developer_Edition/Reverting