Adaptec, major player in SCSI devices, has diversified into the USB and Firewire area with ease, bringing over its internal PCI boards with the various external connectivity methods that are now taken as common place. Thanks mainly to Apple, Firewire's firmly established but USB has reached its second version without making the 1.1 variety totally obsolete.
It's all in the title and in the picture; you can use the Xhub 2 (Adaptec part number AUH-2000) to split any USB port into a pair. As implied, the aim (and recommendation) is for the faster USB 2.0 speed. Since it will give you one additional port, it's really aimed at laptop owners who will generally only be bestowed with one slot of each type. They may have a situation where another port will be needed, like using keyring storage to back up if you've already got a printer or scanner attached, to use one example of working on the move.
It all depends on the convenience factor, as the Xhub2 is light as a feather and so laptop users should snap this up. The portable alternative from Adaptec will take up a precious PC Card slot which may be needed for other devices. At £19 plus delivery it's encouraging that you're paying around the same price whether it's portable or for a desktop. Full sized PC users should just get an internal PCI equivalent for an average £5 extra which will provide four extra ports instead, that's if their motherboard chipset doesn't provide up to eight like VIA's KT600.