Devil is non-modal. As soon as you type a complete key sequence, Devil executes the command and gets out of your way. There is no toggling back because Devil deactivates itself automatically on command execution. And then Devil remains idle until you type the Devil key again.
I believe this was their point, see gp
The advantages of modal systems are more apparent once RSI gets to your wrists.
Well, not me; I moved the modifier key to a foot pedal.