Angry Birds

Most of the time I tend to be fairly serious, so I decided to lighten up a bit and try playing Angry Birds.

I hate to admit it, but I don't get the game.  No, I understand that it's based on laws of physics and I comprehend the principles involved in judging trajectories and impact velocity.  What I just don't get is why tossing irritated birds at green pigs is fun.

So what is the appeal?