Yes I am.
I am thinking about putting together a magic item set, and considering using the set abilities, which are supposed to be 10-30% of the value of the items required, to enable using the activations "faster". Instead of 3-5 items, all requiring swift actions to use, allowing some items to be activated during the same round.
I am trying to decide if that is reasonable.
Of course with existing items there is the question of how much it would change the cost of the item to have limited use activations be faster than those listed for the item.
"Zero" does not seem to be a reasonable cost, otherwise all wondrous items would have free activations for everything.