I also agree with Michael. I just shot 4 rolls of chromes with the 645 + TLA360 combo over the weekend. They all come out great in TTL mode, indoor, outdoor and fill flash. The flash is very easy to use.
The TLA360 even work better with the N1 as it has metric meter. With the ND, it is a little different since the ND has a different flash logic (see manual for more detail). I think the ND tries very hard to avoid over-exposure.
With the N1 in Av mode, I can shoot it wide open with the TLA360. With the ND, it usually does not allow it. Hence, it is almost like in a program mode. However, the result is pretty good. I shot an event and the white dresses and white tux are well exposed. It is very impressive in digital standard. The background is a little too dark as I could not shoot wide open to pick up more ambient night. I guess I would shoot manual mode (flash set in TTL) or Tv mode with lower shutter speed to see what happen.
What is the big deal if the Metz can use in a different system. If you have more than one system, you need two flashes anyway. On the other hand, I am considering to get the Quantum T2 digital flash. It is more powerful with the ability to shoot wireless TTL mode with the Contax.