I identify with my upload on an intellectual level. On the emotional level, I can't really say. Whether I push the button depends on whether I judge "1000 years of agony, then immortality with no memory of the pain" to be better or worse than dying tomorrow, and then on whether I had the guts in the moment to push the button. I want to say I'd go for it, but I don't think I know myself that well.

Oh, by the way: is it one branch of me dying tomorrow and the other being painfully uploaded, or is there only one me with a choice between the two? I interpreted the question as the latter. If it's the former, the doomed branch would probably find the knowledge that another branch of me was being uploaded at least somewhat comforting as the [cataclysmic event] was taking place, and I feel like I'd be more likely to push the button.