That's a great post Hal. I'm going to take some time to think about how to
respond to it in detail. But first I want to say that I think the original
point of decision theory was to justify probability theory and explain
what probabilities mean. (What is the significance of these numbers
between 0 and 1?) So when you talk about something like first person
indeterminance or SSA, or science in general, you have to talk about it in
the context of a decision theory, otherwise the probabilities don't mean
anything - they're just arbitrary numbers.
So my motivation for studying decision theory is to better understand what
probabilities mean (especially when all universes exist). I think Joyce's
book helps greatly in that regard.