Also... as they went through the trouble to specifically indicate the compatible cards, I would imagine there are known incompatibilities with other card types. None of the cards they list would have difficulty over USB. Each of these cards already have similar counterparts that are available to connect directly to USB (vs. using an express card). This would seem most useful for people that may already have express cards that they use in other notebooks so they could use them in a machine without an express card slot... otherwise I would imagine people would just get the USB versions of these devices. USB hubs can obviously connect directly to a USB port, memory card readers are also available for connecting directly to a USB port. RS232 is pretty dated and USB can easily handle RS 232 throughput. I'm not exactly sure what a printer card is... but printers generally connect via USB (or parallel in older machines)... again... very easy for USB to handle. In order for it to work with firewire, they would have to have a hardware translator built into it. I'm sure they would list firewire if it was an option.
