Here is a good article breaking down the baseball count. I really dislike when batters swing at the first pitch, it always irritates me. Apparently its a good pitch to swing at, according to the numbers.
Here is the article: http://sportsillustrated.cnn.com/2009/writers/joe_posnanski/04/22/pitch.counts/index.html
I highly recommend this, its a good read for baseball geeks