Difference between keyframe types

I decided to try out a couple of different keyframe types in Blender 2.62, but I don’t know the difference between the default key vs. breakdown, jitter or extreme. I haven’t gone too much into finding out what each of these does, as I have just been using the default key to do my animating. What is the difference?

keyframe types are only visual properties. they are helpfull in animation to keep track of your workflow.

IIRC the only difference is the color of the diamonds in the dopesheet action editor.

You know what would make them more useful? A way to switch modes of the Up/Down keys. So it would be like Ctrl+Shift+Tab for Snapping Mode or Edit Mode Ctrl+Tab for Select Mode. The menu that would pop up would have all the keyframe types in it, and then the next time you press Up it would ignore the other Keyframes and hop only to the ones of the type you chose.