Off of the top of my head, torture and similar very unpleasant things are useful for at least two purposes.
As in this post, you could attempt to quantify how much you value something (in this case, effective immortality) by how long you would be willing to exist in an extremely uncomfortable state (such as being tortured.)
Similarly, if someone is attempting to make certain absolute statements (such as "I would never kill another human being.") regardless of circumstance, such conjecture can be used to quantify how much negative utility they attribute to committing such an act.
If you feel severe discomfort in being in a conversation where someone is using torture as a hypothetical, I suppose that you could either leave the conversation or ask them to use a different hypothetical, but the whole point of using torture as a hypothetical in such a case is because it is extremely unpleasant, so their alternative, if chosen well, maybe be equally discomforting to you.
I have been trying to absorb the Lesswrong near-consensus on cryonics/quantum mechanics/uploading, and I confess to being unpersuaded by it. I'm not hostile to cryonics; just indifferent, and having a bit of trouble articulating why the insights on identity that I have been picking up from the quantum mechanics sequence aren't compelling to me. I offer the following thought experiment in hopes that others may be able to present the argument more effectively if they understand the objection here.
Suppose that Omega appears before you and says, “All life on Earth is going to be destroyed tomorrow by [insert cataclysmic event of your choice here]. I offer you the chance to push this button, which will upload your consciousness to a safe place out of reach of the cataclysmic event, preserving all of your memories, etc. up to the moment you pushed the button and optimizing you such that you will be effectively immortal. However, the uploading process is painful, and because it interferes with your normal perception of time, your original mind/body will subjectively experience the time after you pushed the button but before the process is complete as a thousand years of the most intense agony. Additionally, I can tell you that a sufficient number of other people will choose to push the button that your uploaded existence will not be lonely.”
Do you push the button?
My understanding of the Lesswrong consensus on this issue is that my uploaded consciousness is me, not just a copy of me. I'm hoping the above hypothetical illustrates why I'm having trouble accepting that.