The first iPad Camera Connection Kit we've seen in the wild has apparently turned up for a quick unboxing demo, courtesy of iPad owner Jerrod H. His photos show the two dongles themselves - one USB, the other with an SD card slot - together with an image of the import process and another of the iPad offering to wipe the transferred images from the memory card.
Unfortunately, it doesn't sound as though Apple have left the USB dongle open to anything but digital cameras. We'd hoped to be able to plug in other USB devices, such as USB drives, keyboards or maybe even a hub, but it looks like only photo imports will be supported. When plugged in, a transfer dialog is shown allowing you to choose which images to copy into the Photos app on the iPad; these are later sync'd to your computer via iTunes when you plug in the iPad.
Strangely, the Apple Store online still lists the iPad Camera Kit as shipping within 2-3 weeks. However, one of the two user reviews on the product page suggests that their local Apple Store had stock, so it might be worth ringing around if you can't wait for delivery.