I am really surprised by the benefit being switching between machines. For me switching bluetooth devices always has been much harder than just plugging a cable into a different machine. Is the dongle making this easier? Don't you still have to switch what machine the dongle is plugged into?
The keyboard stays paired to one machine over bluetooth, and the other via a dongle (which appears to that computer as just a regular usb keyboard). The dongle is some proprietary protocol over 2.4ghz, it's not bluetooth. I've heard some people in this thread mention that makes it susceptible to interference from places crowded with wifi devices, but for me at least it's been always reliable.
The dongle is instant on. Bluetooth wake up is fast (compared to repairing, or having to disconnect one device to connect another, which I guess is your experience you're comparing to?). So changing to the machine with the dongle in it is instant, the one with bluetooth connection ~1s.
The way I do it does mean the setup only works for n=2 devices, but also reading the thread there seems to be some multi-machine feature in the app if you use that too.
Meanwhile using USB cables to switch means crawling under my desk or having multiple cables cluttering my desk.
