"As a small measure of our appreciation for your help in testing Windows Server SP1 and Windows x64 on the Technical Beta, we are offering active participants a complimentary full copy of Windows Professional x64 Edition. This will be done as a downloadable ISO file only, but will be a licensed copy of Windows Professional x64 Edition. (i.e. not an eval copy). Right now we are making final preparations to have the download, product keys, and other necessary infrastructure. You should expect this offer in the next few weeks."
Woo, more thoughts at my blog, of course.