"First off, let me get this out of the way right up front: This is not the 'fall dashboard update.'
Today the team is releasing a minor system update via Xbox Live. Over the next few hours, when you sign in to Xbox LIVE, you'll receive a prompt to accept this mandatory update. What's in this update? Much like the update last month, the only thing this minor release will do is prepare your Xbox 360 for the Big Button Pad that is being released this holiday. Why do we need to release this update now? Simple: The certification team needs time to test the new controller against the retail hardware/software combination before it hits stores.
One more thing: no new features beyond this big button pad support are included in this update and, once again, this is not the 'fall dashboard upgrade.' When I have firm details on the next major update, I will share them."
Needless to say, if you have anything resembling a hacked 360, you should hold off.