What's the alternative? I'd like some sequence of keystrokes that goes directly to the OS and can't be intercepted by other programs. I want to know that the dialog I'm typing my password into is really the OS.
The overlay would always be available so any app that asks for any sensitive info could use the same mechanism, and I could use it even when the developer didn't think the information was sensitive, or didn't attempt to protect the input channel for any other reason.
A single button on the keyboard is utterly unsuitable for a request for soft reboot unless it is recessed and requires turning the keyboard over.
There were a few iterations that depressed the key, etc.
Overall, I liked the three finger combination because you had to mean to do it.
I will say that using it to login/lock windows instead of rebooting was not intuitive at all.