This has always been one of my favorite articles on the value of the count. It exposes a small fallacy about the value of being ahead in the count--that being that these studies usually only take into account counts where an at-bat actually ends. This is a problem because no hitter can strike out on a 2-1 count (for example), but they can and do on a 2-2 pitch. This means there are fewer ways an at-bat can end on a count with less than 2 strikes. When you remove this bias what you might find is that hitters do better when they see more pitches--regardless, to a degree--of count.
Ultimately it says that pitchers who get ahead in the count do better primarily because they increase the likelihood of a strikeout, not necessarily because the batter makes any worse contact.
http://ise.tamu.edu/people/faculty/B...0by%20count%22