[thejeff]

Technically some of those don't autocast the spell, but the effect is the same. They don't stack. It's more that some things are just effects. You either have luck or not.

Charcoal Shield and I think, Boots of quickness show the effects outside of battle, so they don't just cast the spell.

Rime Hauberk and Crystal Shield do, not sure what else.

Occasionally the difference is important. Luck and Missile Shield effects from items protect outside of battle, which they wouldn't if it was an autocast.

There was also a thread at one point about using the autocast items with Communion/Slave matrices to get effects on the slaves.