Well, that was my biggest problem with the C. Bale performance. He was a believable butt-kicker, but a terrible everything else. Once you stick a cowl on affleck, he'll be a believable butt-kicker still capable of portraying B. Wayne.
At least Ben Affleck has a love of comic books and has some huge comic nerds to research with, like Kevin Smith and others... We'll see how this goes. I think no matter who plays Batman its too soon... since The Dark Knight Trilogy was just finished.