In order to better understand the quality of life of one who lives in such a dire condition as Terri Schiavo, I suggest readin Dalton Trumbo's great novel "Johnny Got His Gun." The book traces the inner-thoughts of a WWI soldier that get nearly blown apart in the trenches. For years, lies in a hospital room, unable to communicate or move on his own or any other basic human action. He basically goes insane because he is trapped in his head and stuck on a bed for a time that is immeasurable to him. While this is a work of fiction, the story is all too applicable in this case.
If there is a hell, I guarantee Schiavo's parents will be going and their torture will be to lay on a slab, unable to convey any thoughts to others, for thousands of years.