I am happy to report that object-object collisions seems to be fixed in 1.5. Before, and dating back at least to March, LSL collision states would not always trigger between object and object.
Example: I shoot at a wall 10 times with a gun whose bullets are programmed to llDie() on collision. Pre-1.5: about 1/3 of the bullets will randomly bounce off. Post-1.5: all bullets seem to accurately hit and die on collision.
Dan / Kelly - this is what we had chatted about briefly the other day.
Thanks team for sealing up this unusual bug.
-Hiro Pendragon