According to a lengthy phone call between blogger Kristan Kenney and a Technet support rep, you weren't supposed to have access to that offer. If you downloaded keys or software and weren't one of the select few actually invited in my Microsoft, you're a dirty pirate.
Don't use those product keys - they've been blacklisted, and WGA will eat you alive and burn down your house if you try to use them. They can see which keys were provided to which subscriber, and they'll track you down.
I understand that the link was leaked by someone outside Microsoft and they can't be blamed for the mayhem that ensued, but come on. Is this the best solution they could come up with? What's next? Waterboarding to find the original source of the leak?
Oh well. At least we still have our Windows 7 RC to use for free until next year.