This is a minor niggle, but I am sure that OK Google used to let me say 'cancel' to cancel it; now, it's doing a Google search for 'cancel'! Is there a way I can get it to actually cancel instead?
"Thank You." Seems to work. It will stop listening, but also will pop up a list of Ok Google commands. Which is annoying and unneeded. Personally I just say"open (last app)" and resume my life.