Actually, it's HID style USB devices that the ConnectPort Display is limited to. Mice and keyboards fall into this category and are the most used kinds of devices so that's probably why I mentioned just those.
HID means Human Interface Device - simple input devices. Other examples of HID devices are Point of Sale devices like barcode scanners and credit card readers.
This limitation is due to the VNC software that we use to handle the remote access. VNC also handles support for the HID devices through the USB ports.
Our AnywhereUSB (a network-attached USB hub) product can be used alongside a ConnectPort Display to add support for other kinds of USB devices, i.e. printers. The AnywhereUSB supports many more USB devices. Its only limitation is that it cannot support isochronous devices,