I've just sent in our D100 for the firmware upgrade through Nikon UK. Seems simple enough... gave the UK DSLR Firmware Upgrade Hotline a call (0870 060 3515), they booked it into their system, arranged for their own couriers to come pick it up and was told that it would be about a 5-day turn-around!
The D1H firmware upgrade is still not ready in the UK and Nikon UK does not know when exactly they will be ready to take in all the D1H bodies. However, I was asked to book the body in and would be informed via e-mail about similar courier collection details the moment they were all set for the upgrade!
On the whole I'm quite impressed with the service!