Just to add to the 'grinders are great' theory...

They are NOT great if you happen to buy some damp bud. Im talking damp bud, not wet, so its at least smokable. If you try and grind up damp bud, for some reason youll be left with a very small amount of ground-up bud at the end.
They ARE great if you have dry bud. Not ridiculously dry that it crumbles in yer fingers, but dry so that when you grind it, it fluffs up nicely.

WTF was the point of this post? Im not even stoned!