Larry Niven used this as the central idea of his early "Known Universe" books. The problem he foresaw was just what Paq said: Death Row becomes an assembly line for parts. That leads to great benefit for the law abiding public, and the death penalty becomes more common.
Then the leap really occurs, and the death penalty becomes acceptable for most any crime. This supposes some medical advances, but nothing too far fetched. It's an interesting idea, and could be a slippery slope...
Having said that, I say "chop em up"!
