Originally Posted by Psyduck

Point #1: No. That's worse than death. JKR does not go into specifics, but she obviously believes in some kind of an after-life. The dementor's kiss destroys the soul. It deprives the victim, not only of this life, but also of the next.

Point #2: Harry was also "quick to dish out" such a punishment to Sirius. In POA, a few pages before the end of the "Patronus" chapter, Lupin told Harry about the dementor's kiss and that "It's the fate that awaits Sirius Black."
"He deserves it," said Harry.
"You think so?" said Lupin lightly. "Do you really think anyone deserves that?"
"Yes," said Harry defiantly. "For... for some things..."
I doubt that a mature Harry would still feel the same way.