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.