As far as letters to your primitive, modern self about a post singularity utopia and inevitable heat-death go, this is pretty good. I think it conveys the information accurately and (I think) effectively, although I didn't feel much emotional involvement with anything.
so half of matt experiences bajillions of years of post singularity awesomeness but half of him experiences only being plucked from normal experience, then the letter, then death? that sounds lie it is reducing your own utility.
The "half" that gets the awesomeness is by far the larger half. I do feel that I would rather not be put in the situation I described, but I noticed that this could be interpreted as inconsistent with my expressed desire to know that I'm about to die conditional on it being true.
The trick is to evaluate the future with your current utility, not by the utility of future yous. Similarly, don't wirehead or commit suicide expecting to live "quantumly."
EDIT: Actually this might be the wrong trick depending on what you meant. You might have to use the trick of representing multiple instances of a person as frequencies (i.e. not normalized until the end).
Awesome story, though a bit of a downer ending, of course.
(Minor nitpick: The mere fact of entropy increase isn't what dooms us, as such. If entropy kept increasing but max entropy was arbitrarily high so that it could still keep increasing forever without bound, then it might still have been possible to perform arbitrary amounts of computation)
If I understand them correctly, some theories of cosmology imply that the maximum possible entropy increases as the universe expands - and the rate of increase of the maximum possible entropy is actually greater than the rate of increase of actual entropy, so maximum entropy is never actually reached. (If I don't understand them correctly, please correct me!)
The catch though would be issues like "what's the maximum entropy of the largest region of space one could arrange to remain causally connected?"
Maybe I'm vastly over-simplifying it but the way I am interpreting that is to say that even if all of the universe has decayed to heat radiation, that radiation will continue to be further disbursed with the expansion of the universe. So the maximum amount of entropy (amount of dispersal) does always continue to increase. But I don't think disbursed heat radiation could perform any computation.
http://alex.mennen.org/LetterFromTheEnd.pdf
I thought some LW-ers might find this interesting.