Thanks bunches to Helibot for his help, we have pretty much demystified the USBNet feature! It apparently is there to allow some Java games to access the internet. I've run across some that tried to do that.
However, we are still working on a way to use it to access the linux console. To that end, I've got a driver (works in Vista but not sure about anything else as I haven't tested it anywhere else), which will load for the robot's USBNet mode. It's only for development purposes though and includes the libusb-win32 sources and utilities, so you could probably adapt it to other Windows versions.
More information on this and the download is here:
Hope this helps someone! So far all I can do is get it to detect when the robot is connected to the computer in that mode. But read/write is not working because we need to do that via ppp, which is the protocol the robot is using in that mode (via USB).
Other news, I'm waiting on some electronics parts and once I got that (includes header pin material) I will have the stuff to do the serial port hack to my bot. I have the PropPlug now and some wire. So that is another thing that will soon be looked into.
Helibot also gave me some images and script commands for updating Nocturnal's firmware dump script so that images will display when it starts/stops (so you know when to unplug the bot).
All this means that I will hopefully be soon updating the RSMedia Development Kit. I'll announce here when the new version is ready.