Planner or Pantser?

Anyone else just sit down and let the story tell itself? I'm not great at planning things and sticking to them. If I plan them out, they end up changing so much it ends up being a waste of time anyway.

Also, what do you think about Stephen King's notion that you shouldn't keep notebooks full of ideas because all that does is immortalize bad ideas and that if it's an idea worth having, it'll kick around in your head until you eventually use it?

I think I kind of operate that way. 

(EDIT: Fixed the title... was "panster" - Whoops!)