In general, if the build number and the download file size are the same, I would guess they are identical.
I'm not sure Apple would release a file that they called the 'Gold Master' to developers for testing, and then release something different as the full on production release. Apples comments at WWDC seemed to say "Hey, this is our final prod release. Test against this version."
That said, I'm sure plenty of people out there are downloading the full on "legit" file via Itunes..."just to be sure."