Does the USB port work both ways, can I plug Chumby in as a slave device to my computer? That is very useful for software updates, configuring the wireless, debugging, etc.
Probably, but it would probably require a driver be written to support the device (unless you somehow configured Linux on the machine to present the Flash device and make the Chumby expose itself as a Flash drive, and even in that case you're likely not to be able to get away with it without a driver).
Besides, it's got WiFi built in, you could configure the WiFi from the device. I guess it could be useful if you didn't have a WAP or a wifi-enabled machine, but then buying a Chumby seems kinda silly, as the WiFi is definitely a killer feature.
From the sounds of it, there's a lot of software work still to go with the Chumby, and a "Chumby portal" (like iTunes->iPod, PalmSync->Treo, etc) is probably yet to be developed. But, with the device as open as this, it won't be very difficult to code, and it'll definitely be supported on all platforms which is a serious plus.