I liked Zima Blue a lot. I actually think that the most interesting discussion points are not to do with cybernetic enhancement per se.
The final conclusion could be interpreted in many different ways. In the end, Zima shuts down higher brain functions and discards all the complex parts of his cyborg body. It is revealed that he was not a man who was cybernetically enhanced, but instead a cleaning robot which was continuously upgraded. By discarding all of his upgrades, he reverts to being simple automaton with a singular purpose originally endowed by its creator: endlessly scrubbing the swimming pool with a rotating brush. I saw that as a metaphor for giving up the trappings of this world - the pursuit of power, money, fame, material comfort - and reverting back to our original state in the Garden: a creature simply desiring to please and glorify the Creator.
Where Zima Blue differs with the Christian conception is that in the latter, after we voluntarily leave the world, we retain our free will instead of reverting to a mindless automaton. Even in heaven, we will still have free will, even though we are perfectly sanctified and in perfect fellowship with God. In a Christian worldview, such a thing is possible. It seems that in the (nontheistic? nihilistic?) worldview of Zima Blue, even the possibility of enjoying the trappings of this world is an obstacle to true freedom. Thus Zima discards his higher functions completely. It thus promotes a sort of Gnostic or Platonic view of the body. In contrast, in Christianity, the body is not regarded as a worthless distraction. Instead, our bodies will be transformed into the new resurrection body (1 Cor. 15).[/spoiler]