For players, a critical does 2x max damage to the monster they hit.

For a monster, a critical does max damage and wipes out half a player’s healing surges. Doesn’t affect that combat, but it sure makes the players think twice about the next one.

It seems to work well. A critical should be devestating, and I felt that max damage wasn’t quite enough.

Hit Points as a Power and Active Defenses

The DM describes an attack (and the nature of its Effects) The player should then describe how this attack against their character is minimized by luck and energy and skill! On the Player Character sheet you now record the Defenses without the base 10 value and the player rolls d20 instead and adds… it is compared to an Attack value which is static 10 + mods for the NPC’s.

The difference between the description for a failed defense (unless that hit reduces you below 0 hp) and a successful one … is pretty much how desparate or last second it normally seems and/or how much apparent energy it takes to accomplish, even a successful defense could be described as the character getting lucky if that is the pc’s style. The lucky hero, the tough hero, the skilled/agile hero it becomes a descriptive choice. A hit that reduces the character below zero hp should be described by the DM, this is the point were a true wound mechanic comes in to play.

My favorite is so far was elaborated on in Enworld.org , I will have to write it up with my style later. It fits in with the above real well because it involves the player voluntarily accepting a long term wound (long term impairing effect) for there character , in exchange for keeping the hit points.