[Fyron]

Another significant change in Longhorn involves device drivers. In the past, Microsoft allowed customers to use non-signed drivers, which helped compatibility, but caused stability problems. No more: In Longhorn, Users hoping to take advantage of the system's exciting new capabilities will only be able to use signed drivers.

This is extremely disturbing... so now, you won't be able to use drivers from companies that do not pay Microsoft loads of money to get the driver signed... super.