Peng and I have a paper accepted at the KR 2014 conference on how to identify the best shot in a given situation. We do a qualitative analysis of the stability of the castle and assign a heuristic value to each block, depending on how much damage it will cause when hit.
P. Zhang, J. Renz, Qualitative Spatial Representation and Reasoning in Angry Birds: the Extended Rectangle Algebra, Proceedings of the 14th International Conference on Principles of Knowledge Representation and Reasoning (KR'14), Vienna, Austria, July 2014.
You can download it here: http://users.cecs.anu.edu.au/~jrenz/pap ... z-KR14.pdf
Have a look and let us know what you think about it.
Jochen