The results are lovely. What makes you prefer it to the Nikkor 35mm f/1.8S?
(I don't need one, I don't need one, I don't need one...... 
)
Of course you need one. As far as I am concerned, 40mm always felt natural - in fact, 20, 40, and 58mm (quasi 60) all do, more than the usual 28 (or 35), 50, 85.
One reason I did not buy that one is, the Z40/2 is sweet (so is the Voigtländer 40/2 and its close-up complement).
The other reason is, when I went to buy it, it was out of stock while the 50/1.0 was there and is darn good, even wide open. After testing it for 1/2h I could not part with it.
I may get back and add the 40/1.2 to my inventory, but there is some redundancy - the 50/1.0 is equally a well-built MF lens, just a bit longer and bigger. Another redundancy is with the 50/1.2 Nikkors, dreamy wide open, very sharp from 2.0, while the 50/1.0 is more consistent with its high contrast through the whole range, remindful of the Noct Nikkor.
But coming back to your case: if you have no 40mm, resistance is futile. Surrender while stocks last!
