Nikon has done a piss poor job of servicing their scanner software if you ask me.
No argument here. However, it's IMO better than the two main alternatives. VueScan has the worst interface and lousiest documentation of any program I've ever seen on the Mac. And Silverfast is outrageously expensive and needlessly complex, with an inteface only a software engineer could love.
Their scanner driver won't work on Mac OS Leopard at all.
Completely untrue. It works on my Leopard system on both an older PowerMac G4 and a three-month-old MacPro tower.
I initially had trouble with Leopard on both of these systems, with NikonScan not recognizing my attached/powered-on Nikon 8000. An exchange of emails with Nikon support revealed the problem--the software won't tolerate any other Firewire device being attached and turned on, even if it's "ejected" like you can a Firewire ExtHDD.
This is inconvenient, but not fatal. Alas, with the scanner market shrinking, it's hard to see Nikon doing much to support NikonScan thru the next version of Windoze or MacOS to come down the pipeline.