Just had an interesting thought strike me. It's occurred to me in the past that certain injuries, broken bones, snapped tendons, organ failure and so on isn't particularly reflected by the hit point structure--though because I don't see any system being an improvement on the HP idea, I haven't seen a simple, easy way of handling those injuries. Thus, they are usually "overlooked" while gaming.
Part of the trouble is that healing spells ought to be able to "fix" those things as easily as simple wounds. If a character heals at 1 hp per day normally, then the first level spell, cure light wounds, serves to heal anything which might be conceivably healed normally in six days.
Of course, a broken ulna (bone in your arm) takes twelve weeks to heal, but who's counting, right?
What if we take the very simple approach of saying that certain injuries (how they occur is your problem) require 10x as much healing to repair? For example, suppose your 2nd level ranger with 22 hit points sprains his wrist. And let's suppose we call those points which heal at 10% normal speed as "hard points." To give some measure to the sprain, let's say a sprain is 1d4 hard points...we'll roll the dice and assess the damage as "3".
Normally, to heal 5 hit points, it would require 5 days of rest or a simple healing spell. But in this case, 3 hard points require 30 days of rest. The ranger is temporarily at 19 hp maximum, adding 1 hp more to his maximum each time that 10 equivalent hit points are cured. On average, that would be six days of rest and cure light wounds spells to bring him back to normal.
Not much of a hassle for a sprained wrist, but what about a broken leg? Or gall stones? (what, you've never given your player gall stones?). It would be hard for a 2nd level player group to get 200 healing points together.
The rule has, I think, interesting possibilities.