I had the chance to install these cranks last night; they rode just fine for a couple miles home from the bike shop. Friction did not help much to hold the chainrings in place: the large ring slipped a bit backwards relative to the crankarm and small ring. It seems to have found its home once the the bolt hit the edge of the hole, though.

Still hoping this'll have decent reliability, but I'll be checking it carefully from time to time. If this were fixed-gear, I think it wouldn't last at all because of the back-and-forth rocking of the large chainring. (If I were really concerned about it, some longer chainring nuts would help fix the big ring in place.)