I am running an external USB sound with a c-media chipset for wiring up a microphone for voice control/bluetooth hands-free. Works perfect, no skips, glitches, or standby issues. I'm thinking the Eee may be able to run those new LCD's. Not too sure... Maybe someone else on the board has tested one of these new USB LCD's with the Atom 1.6ghz chipset?
What I have plugged into USB isn't exactly anything to require much CPU power at all.
Touch screen, very very minima data transfer or processing involved.
Sirius interface, hardly any processing power needed.
GPS - yet again, barely any data transfer or processing needed.
Memory card reader, rarely gets used, probably can use a bit of system recourses when transferring lots of files at a time.
iPhone - I don't have itunes installed, just plug it in to charge it, no CPU power required.
Startup/shutdown controller - doesn't transfer data, only uses the USB port to sense the power on/or off state of the computer.