The catch is you need to be ready to develop for Windows Phone, and ideally target the Nokia devices, but there's no word just yet on what the commitment is (Maybe it's just a pinky promise?).
1000 handsets are sitting in a truck just outside the ExCeL center, waiting for the Developers post-event party. No word on the other 24,000, but with developer events and significant community outreach planned for the next twelve months, these are sure to be distributed to ensure an amazing developer experience... everyday.