That said, no-one would ever engineer an augmentation that you can't manually turn off somehow or at least something. And even if you can't, there are plenty of things that are physically impossible to survive no matter how much indestructium alloy your skull is coated in. If you're bored after the first few millenia, just hurl yourself into the sun. There's no way an immortality upgrade could do the same stuff as an immortality "curse" from fantasy fiction.
Well, then you wouldn't be immortal, would you?
You'd be something like "practically immortal" or just have an indefinite lifespan.
Both of which appeal somewhat, but not all that much to me. I'd still very much like to die at some point, and I don't see a lot of reason for putting it off too far past my time.
Besides: Common availability of "immortality" augments would lead to a horrible surge in social conservatism which would just make me so depressed.