derelictjay
Explorer
I've ran one Eberron campaign using them. They don't overbalance the campain as they are an expendable resource. And in a lot of ways they actually help the game along.
They can also very well create a kind of heroic effect, when the chips are down. In one particular epic encounter, all the PCs were still standing but where all low on hp, spells, and other resources, (at this point I politly reminded them of action points) so the Actions Points started flying; saves, to hit rolls, you name it, they used them (I didn't allow my players to roll the AP after they saw d20 roll), by the end of the encounter my five PCs were down to 2 or 3 APs between them (5th level characters), but were still standin. After that they I never needed to remind them about action points at all.
They can also very well create a kind of heroic effect, when the chips are down. In one particular epic encounter, all the PCs were still standing but where all low on hp, spells, and other resources, (at this point I politly reminded them of action points) so the Actions Points started flying; saves, to hit rolls, you name it, they used them (I didn't allow my players to roll the AP after they saw d20 roll), by the end of the encounter my five PCs were down to 2 or 3 APs between them (5th level characters), but were still standin. After that they I never needed to remind them about action points at all.