UPDATED: Well, Game Center is gone in the release version,
We keep getting asked if there will be a difference between the iOS 4 GM (gold master) seed released to developers at WWDC 2010 and the final GA (general availability) version that'll be released to end users sometime today.
Maybe. Other than the former being intended for developers and the latter for end-users, we don't know though we guess they'll be fairly close (so apps developed under the GM don't run into problems under the GA). Apple could have found and patched a few trivial bugs, removed debug code, or made a few non-app impacting tweaks. The GM seed may also be read differently in iTunes and not prompt for future updates (i.e. 4.0.1, 4.1, etc.) the way the final release will. Or they could be binary identical.
Until Apple releases it and elite code scourers do their thing, there's just no way to know.
(And if you don't know what anything in this post means -- we envy you. You shouldn't have to).
Now relax, grab a spicy drink and some popcorn, and resume the great waiting game...