Interesting original thought extension, Ed. I would say that "sentience" is an (imperfect) term from (imperfect) Cognitive Science, but if you boil it down to logical calculations and/or behavior, then I would say it's true machines have sentience, as do animals. Basically, my matrix looks like this:
Code:
Logic Language Identity Experience/Consciousness
Human yes/much yes/advanced yes - noisy yes
Animal yes/some yes/basic yes - simple yes
Robot yes/lots yes/logical maybe no/artificial
The lower-right cell is the clincher for my moral decisions. Go ahead and power down your computer. But please be kind to animals.