I'm pretty sure hoovedawg tried one of his programs (Think it was the unbreakable abs program).
However he hasn't posted in a while, so I don't know if he'll see this.
Maybe PM him.
I regularly read Doyle's blog. As well as many other baseball related blogs. He usually has some good stuff, with different articles by himself and others, possibly an exercise, I've even seen a "Power chile" recipe.
The "7 secrets of successful hitting free report" was a worthwhile read, and he points out some stuff I don't necessarily think about when working on hitting.
As far as baseball specific although he does advertise his programs effective for all players, but I will point out Doyle was a hitter.
To my understanding, he is a strength and conditioning instructor, and hitting instructor primary.
He doesn't really dip into the depths of pitching, which is fine, because there doesn't seem to be that many guy's with programs for fielders and hitters.
I expect Doyle's programs to be good, for me at least, I would combine them with some more pitcher specific stuff, such as the new Tuff Cuff book, which I will be investing in shortly :-).
Edit: Fixed my pathetic grammar and wording.