STEPS TO REPRODUCE: In a fresh profile... 1. Tools | Set up Sync 2. Click "Connect" button, below "I already have a Firefox Sync account" --> Now you're on the "Add a Device" screen --> Note that "Next" (lower-right corner) is grayed out 3. Click "Sync Options (lower-left corner of dialog) 4. Click "Done" EXPECTED RESULTS: "Next" still shouldn't be available ACTUAL RESULTS: After I leave Sync Options, "Next" has magically become available. (If I click it, it drops me to the "I don't have a device with me" screen.) This might be remedied by just removing "Next" altogether, since it seems to have no function under normal use. It's initially disabled, and when you actually add the device on an already-connected computer (when I'd expect 'next' to maybe become enabled on the new device), the dialog just advances itself automatically to the "Finished" screen.

Good catch! Will fix. I think having the Next button there makes sense as it indicates that there is a page after this. It's also there in the original mockups.