USB powered devices such as iPod, card readers, keyboards, must be unplugged prior to shutdown or sleep. External hard drives, though self powered, will always pose a problem, and should not be connected to the PCI card. My HP printer connected to my pci card causes no problems.
For USB 2.0 devices, self powered units such as printers, scanners, readers, etc., leaving the usb connected during shut down or sleep is possible, depending on the device. If you have primarily USB 1.1 components, and are in need of more ports, use a powered hub instead of the pci card.
All that you can do is to buy a card, and then try your components. I think your going to find that the opinions and the results of use are a varied as the components that are connected.
