No experiences with them, the cheaper ones around here only support PS2 keyboard and mice, no USB.
I use a ATEN US421a, for switching a logitech unifying receiver. Switch time is about 4 seconds.
However it’s used only on emergency, as I mainly use a “soft switch”: Maxivista, extending my screen real estate of the one machine with the screen of the other, with mouse/keyboard travelling to the extended screen automatically, either when the extended screen is used, or when working with the other computer.
Have a look at synergy, or sharemouse for softswitching.
If you are working with multiple computers, there is every reason to network them. I have two laptops, both equipped with a rme HDSP digiface. On the “master” laptop, I hooked up a dell u3011 and two nec 2080ux via usb3 displaylink, so I have a screen real estate of 1920x1200, 1200x1600, 2560x1200, 1200x1600. I’m using maxivista which adds the screen of a second laptop as additional screen to the first computer, extending the screen real estate by another 1920x1200. Plus, when using iDisplay on the iPad, adding another 2048x1536, touchable.
The one mouse on the master laptop travels across all these screens, keyboard working accordingly on all acreens.
Audio travels through ADAT of the HDSPs, the second laptop basically is my mixing desk. Audio travels also through ethernet, using Vienna Ensemble Pro 5, utilizing both laptops as VST hosts. Multiple Midi devices are hooked to both laptops, midi travels through copperlan, so everything is available in demand on both laptops.
The hardware switch only is there, when the master laptop isn’t turned on, when doing software development stuff on the second laptop, for example.
I want to add another laptop to this setup, as new “master” where all the DAWs are running. It won’t be equipped with another soundcard though, I currently develop a solution to use any asio soundcard on the network anywhere as asio soundcard on any other computer in the network, using copperlan.
There really is no reason to not network computers…