Thanks for all the replies. I'm sure just like everyone else I can't wait to see how the rules actually handle this new mechanic. Until then though, I'll remain skeptical that that any resource that gets replenished per day, or any in game time, will help with the combat, rest for a day, repeat syndrome. Of course, DMs can do their best to disuade these issues, but I'm hoping that new rules might help as well.
Perhaps "per session" is not the best way to go, or maybe not the best descriptor. Would "per adventure" be better? This might allow an adventure publisher or the DM themselves great latitude in defining the terms?
Another idea would be to have the characters kick butt powers have certain prerequisites, defined circumstances, or prolonged consequences. The current Cleave feat would fall into this kind of definition. The 4e desciption of the dragon combat where the dragon gets to use their breath weapon after falling below half hit points would be another. Or something like an ability "Incredibly Powerful Power Attack" which could automatically do x100 damage, but the weapon used is destroyed might be another. Is that too Final Fantasy-ish?