Thank you all for your kind comments!
Jim, my D100 is off for Firmware 2 upgrade (unless there is a newer version) - I have been shooting it all year and didn't want to risk it being away until my diving season was finished.
Don, the lens has very similar dimensions to my 16mm FE. So I am sure I will (eventually) just use it straight behind the Subal FE dome.
Craig, you might be interested to know that the rear filter holder is different from the 16mm and can only accept cut pieces of gels.
Kasey, I have no idea on availability. My local camera shop is well connected, but Southampton (a small city on the S. coast of England) is hardly the centre of the photographic universe. I ordered the lens about 2 months ago, hoping to have it in time for my Red Sea trip a couple of weeks ago. I imagine that world-wide availability is pretty similar - I'd imagine Nikon will be working through the pre-orders for the next month or so. I'll ask - I was going to pop in there again today to try the lens on one of their S2s or D100s!
I wonder if they will let me borrow one overnight to try it in the local dive pool?
Alex