Overbay won't ever hit 30+ HR's, he's not that kind of hitter. Even in AA he wasn't the power type. If you want Sean Casey type of production in the future he will be an alright prospect. I would rather have him develop into a Mike Sweeney type hitter who has some power and hopefully hit over .300 with 25 hr's who doesn't strike out and can spray the ball over the field. But that won't be for a few more years at the earliest IMO.
Oh, he's not overrated. He's not really a consideration really unless you are in a deep league or an NL only league.
"Relievers are like volatile stocks. They're the one asset you need to watch closely, and trade for quick profits." --Billy Beane