Product is good, the only downside is that it has no indicator on what is the current computer the usb is routed too. Therefore when you turn on a computer you don't know if it is connected or not -- as I have a operating system switcher that chooses the default after 5 seconds this has caused me some issues if I am routed through to a different computer. But apart from that, this is a good cheap device.
I use it without a power source, I have a wireless nub plugged in and switch my keyboard and mouse between a Windows PC and a Linux Server