From The Openness of God:

The difficulties with perfect being theology do not, in my view, stem from the assumption that God is an absolutely perfect being-that he is “whatever it is better to be than not to be.” Rather, difficulties have arisen because people have been too ready to assume that they can determine, easily and with little effort, what perfection is in the case of God-that is, what attributes a perfect being must possess. Yet it clearly is no simple matter to say what is the best kind of life for a human being or what are the ideal attributes (or virtues) for a human being to possess. So why should we assume that this is simple in the case of God? I do not think it should be taken as obvious, without long and thoughtful consideration, that it is “better” for God to be temporal or timeless, mutable or immutable, passible or impassible. So if we are going to object to Plato’s argument, we need not reject perfect being theology as such; rather, it is the application the argument makes of divine perfection that we must question.