I have been using action points in my game since they were introduced in ECS. While I use them pretty much as written in that book, I also found something on I think it was Malhavoc's forum about using APs "before" you roll as opposed to after. So the new house rule has been that if you use an AP BEFORE you make your roll, you get to add 1d10 to the roll (scaled up appropriately as normal, i.e. when the 1d6 becomes 1d8, then 1d10 becomes 1d12 etc). This has been a great success, and encourages players to make use of APs on rolls they absolutely MUST succeed in. In actuality, the most common use of APs is naturally in combat, for making sure they hit, and sometimes allowing for that all but impossible hit to actually have a chance. Strangely enough, the second most often use for spellcasters at least is to overcome Spell Resistance.
I also allow some of the players to spend an action point to get "dreams" or "visions", i.e. GM clues about their current problems and the like. Paladins and other divine casters (I do not allow clerics in my game) find this ability especially useful when confronted with some action that may or may not fit with their beliefs/alignment. Keeps the number of attonements needed at a minimum.
Lastly, for those who spend an action point on a combat roll BEFORE they roll, roll a natural 20 AND a natural 10, I usually come up with something extra special in their crits (since I DO NOT confirm crits...a crit is a crit, as long as it also hits). We just started using the critical hits/fumbles tables printed in the Dragon Compedium, so I don't know how this will effect that yet.
skippy
The GM of The Cursed Earth Campaign