I see Willie as the type of manager who is very faithful to veteran players and more skeptical of younger players. Maybe skeptical isn't the right word. It seems like Willie wants the younger players to go out and prove themselves worthy of something better, whether it's an advancement in bullpen confidence or a higher slot in the batting order.
Mike Cameron and Doug Mientkiewicz, while good players in their own right, are weaker hitters than David Wright. In reality, the Mets biggets problem is going to be the top of the order's inability to get on base. Mike has a nice article on just this topic over at MetsGeek.com today.
Frankly, I'm willing to give any of Willie's lineup machinations the benefit of the doubt for a few weeks. If Wright is still hitting 8th and Reyes/Matsui are sporting .300 OBP's by the end of May, Willie best realize there's a huge problem and go about rectifying it.