For a free game, this is really quite a lot of fun.
Admittedly, I had a blast with this one and was completely impressed with the scaled of the game considering it was a free offering. One might be hard pressed to find another free game and lengthy and consistently fun as Angry Birds.
I tend to be the type who enjoys a game with a really good story. However, when you have a phone it's not often the case that you'll find such an option. As such, you wind up with a lot of random, and often terrible, puzzlers that just aren't worth the time after a few levels. With Angry Birds this just isn't the case as they consistently keep improving the boards as well as putting more bird attackers in your arsenal to help you take care of the enemies.
This one is definitely worth playing and has created such a buzz beyond the game it has proven that the developers have what it takes to really produce some high quality work!