Leopard, DuelAdapter, Kyocera KPC650 and Verizon
Just works! I gambled and bought an open box DuelAdapter PCMCIA-ExpressCard bridge from Sewell Direct. No drivers to load on OSX Leopard, but make sure the switch on the underside of the card is in position ‘A’ (Mac mode) like it says in the manual. That's it. The VzAccess Manager detects the card as normal. I tried a few other Type-II cards I had lying around and they behaved as expected, which is to say, they registered but not all of them did anything, that being a matter of having an appropriate driver.
The NationalAccess service is no slower, or faster, than it was with a PCMCIA slot equipped Mac running Tiger. At home I've seen a peak of 310KB/s down, 105KB/s up. On the train I usually see 30-50% lower (sometimes much lower) which is still fine for ssh and casual web-browsing.
My only gripe is that the DuelAdapter is big. Not including the size of the expresscard itself, the cable is 9" long and the PCMCIA carrier is nearly 6" long and 3" wide so it doesn't fit on a standard tray table with the laptop. I'm thinking I might solve this with a piece of medium-duty velcro on the lid of the laptop which would also orient the card in a good position.