Has anyone noticed a difference in tire wear? How about the chances of getting chunks taken out by a sharp spot? Logic seems to tell me that a squishy tire's tread would be less likely to be rigidly pushed into a sharp spot, but more likely to try to "hold" onto a sharp edge of a ledge instead of cleanly rolling off.

Airing down seems like it would make for more exposure to the sidewalls by rolling them outward and closer to the ground?

Airing down for Black Bear Pass in Colorado I ended up with a few chunks missing from my tread. The Chute area was similar to what I do here in CA, and I normally do not lose chunks from my tire treads. These are new tires though, so I don't know if it is the tires or the airing down that is more at fault.