I've been thinking about ideas along these lines a bit recently. I think, if this kind of thing is possible (i.e. branches of low probability never go to zero, and are always realizable), it would be important to make sure that all of your probability mass is crisply divided with some going to universes where all consciousness is quickly extinguished and some to universes that continue with whatever properties you want, with little to none leftover for other possibilities.
In other words, quantum suicide is a bad idea for the individual (you leave around mourning loved ones), but perfectly fine and acceptable to exploit on the civilization level.
I'm sure you've read it, but to give everyone else context, here's the paper on civilization-level quantum suicide.
Also very relevant to this discussion is the paper "Many-Worlds Interpretations Can Not Imply ‘Quantum Immortality’" [pdf]
Edit: Original link wasn't working, so I uploaded a copy.
The universe is running down - there are only so many sources of negentropy that can be used for the work of life and intelligence. But thermodynamics is a statistical process, an average of a great many small processes. The standard model of MWI makes a certain hash of statistics - in a vanishingly small number of Everett branches, those statistical averages go right out the window: all the air in a room flies to one side, or an egg unscrambles itself.
In those universes in which life continues to survive after all the stars burn out, and all other known sources of useful energy have been turned into waste heat... might it be possible for said life to continue to survive in at least some timelines, by feeding on thermodynamic miracles?
And, at least as important, which forms of thermodynamic miracles are the most common, and which are most potentially useful? (After all, in any given volume of space ,a few electrons appearing out of relative nothingness is much more likely than an entire Boltzmann Brain appearing, and depending on how stable the matter-energy substrate that life at the time is using to maintain itself between miracles, said substrate might decay before some kinds of miracles ever occur...)
Edit: Question posed in recent 'Open Thread' at http://lesswrong.com/r/discussion/lw/jww/open_thread_1824_march_2014/api5