Heh heh, I guess if you haven't followed the news for some time it mightn't be very obvious, but from the pictures this is what I got:
DVD kit: Intermediary between the DVD drive's power connector and the power supply, since the power connector for the DVD drive also has the eject line, they added a button to their panel so you could open/close the tray. Also, (IIRC) the mode switch is something that you need to send to it in order to unlock it for the PC?
HD kit: Allows you to use 12V (molex) or 5V (USB) to power the 360 HD, and a SATA connection to plug it into the computer.
Yup.