Yeah, I thought he was great on Carnivàle too.
There's a little more information floating around now. Apparently Knepper's part would be Cassidy. Which I would be more than fine with!
And thanks Yoda and Dread!
I'm really excited about this, hope HBO will pull it off. Read that Robert Knepper might be a series regular. He's great on Prison Break, I think he would be a good fit for Preacher too.