My Guess would be all the problems with rev 1 boards fixed I.E. memory , sound, fan issues, etc etc
if you compare the two pictures off the gigabyte site you can see quite a few component position changes and some additional capacitors and other surface mount components.
just a hunch that they used all issue one owners as like beta testers.
i have pointed them towards this forum in the past along with other forums, so maybe they do read the posts