A lower standard of health. of course if everything else you do is unhealthy then its not going to make a difference whether you smoke or not.
I almost brought health up too but then I thought about it...
Most of us [in the western world anyways] would need to change our diets and exercise patterns first when talking about making positive health changes...Weed doesn't even compare to those things in terms of making an impact on our health.
So really there is nothing besides $$$$$$ to be gained by quitting.
Maybe getting over a mental reliance if you have one? Which if you are a seasoned toker, most of us will have developed some sort of reliance.
But it's only because the herb is so damn helpful for so many things!--sleeping, mood, stress, eating, pain, stomach issues and so on...
How could you not develop a reliance on such a powerful herb?!