I think it's a good pickup. It's not crazy to think he could figure things out at 27.
Still, it wouldn't shock me to find out he's got an injury. The walks have always been a problem, but he lost the ability to overpower batters in 2008. He stopped striking guys out and getting pop-ups, started giving up homers and stopped throwing as many ground balls.
Contrary to his reputation, Cabrera is a decent guy. He's not crazy, he just can't throw the ball over the plate.