Eh, I was talking more like an event where a crumbling dungeon means the players need to keep moving and can't full attack. (Except, for that example, the speed boost still rocks.)

Having a bunch of NPCs decide to hose you for using a plain game mechanic seems like the relationship between the players and the GM is adversarial. I'm fine with 90% of the fights being formulaic cakewalks. Means everyone doesn't have to pick the absolute best classes and options in order to be a part of the action.