A few weeks
ago I bought a few USB serial port adapters, and they work fine on a
variety of PCs running various versions of Windows. Not, though, on a
Mac, which doesn't even see them.
Did they 'just work' or was a driver downloaded off the net to make them work?
The curse of Windows is every vendor doing things their own way, and the need
for thousands of incompatible drivers. You can extend this to USB drivers as
well. A USB async adapter can be implemented a bunch of different ways, going
as far back as Anchorchips devices that squirted code onto the adapter, up through
the current reduced cost devices that barely offer any tech docs on how they
work.
Vendors really only care about Windows support, and grudgingly give out info
to driver writers (or they have to reverse engineer the hardware to do it).
They also want to lock you into their device, so they have no interest in common
drivers.
Getting back to the original topic, as long as the protocol for the floppy adapter
is documented so that people can write USB drivers for it for other platforms, it
should not be an issue.