"[panentheism is] literally, the teaching that 'everything is in God.' Panentheism differs both from pantheism that identifies God with the world and from traditional Christian theism that speaks of God as creator of the world out of nothing. According to panentheism, God and the world, while distinct, are nevertheless parts of a single ontological whole. Some world, if not this world, is necessary to God, and apart from a world God would be only a abstract possibility. For panentheism, God is not only affected by all that happens in the world, but i is through the world that God becomes concrete and reaches full self-actualization" (page 419-420).According to panentheism, in other words, God is distinct from the world but he's just not himself without it. God may or may not have created the world in such terms, perhaps not ex nihilo (out of nothing), and the world resides in God (which may be quite different than saying that God resides in the world). Therefore, everything affects God and God (and this is why panentheism is so important for process theology) "reaches full self-actualization" in the world. William Placher offers a much more concise definition, "God is not identical with the universe...but also not separate from it" (page 380)
Now the beauty of this perspective is that God is not somewhere "out there." God is and can be discovered in human experience and relationships. As Paul said, "all things are yours...you are of Christ, and Christ is of God" (1 Corinthians 3). God is not in competition for our affections with everything and/or everyone else, in fact, He lives and moves in everything else. As Paul also said, "For in him we live and move and have our being" (Acts 17:28). But I think a problem arises when we consider the eschatological implications of this perspective. Where does our help come from? If God is affected by the world in every circumstance and if it's in his being affected that God becomes himself then eschatological hope must also reside in the world in one way or another. It comes bubbling up from within God's experiences. God stands with us in the present, having experienced the past, looking into the future.
But if God is "wholly other" and separate from his creation then he can offer some rescue and a real eschatological imagination. But this God, as wholly other, cannot simply be a being who resides separate from us in the present, otherwise all of that idolatry paranoia and the sense of deistic abandonment come fully alive again--the very problems which panentheism seems to handle. Even the incarnation makes little sense of this if God remain "wholly other" as a being who exists throughout time. But perhaps we can make sense of this the same way Wolfhart Pannenberg and Jurgen Moltmann did.
According to Stanley Grenz, Moltmann and Pannenberg "sought to avoid speaking of God as an existing being among other beings... To accomplish the needed transformation of theology, they shifted the focus...Instead of the past, they looked to the future to provide he 'location of God'" (page 79-80). God, then, is "the power of the future" (Moltmann, The Experiment of Hope, page 51), creatively offering rescue and imagination from an eschatological perspective. Therefore when we experience God, it is the future opening to us and bursting forth into the present. The incarnation is God taking on the flesh of the present and inviting us to dwell in his kingdom, his future imagination for the world, what Dallas Willard calls "the eternal kind of life now" (page 1).
Thus we engage the questions of God's existence, our worship of God, and our experience of God not from the past and present perspective--what did God do before the creation of the universe? How is God affected by what's happening now?--but from the future perspective. We ask the questions of creation, transcendence, and immanence from a perspective of eschatological hope--What's God's hope for the world?--and thus we can understand how a God who has opened himself up to the universe, in such a way that we can even experience God therein, can offer the rescue and hope from outside that we really need. We need a God who offers salvation which bubbles up not from within but from without, a kingdom which is "not of this world," but who also dwells in the present world as that future rescue taking on flesh of the present in Christ Jesus.
The God who is "wholly other" and who is radically separate from his creation has also radically opened himself to his creation, taking on flesh to offer salvation and to bring His Kingdom which is "not of this world." It's not haphazardly that we find God in relationships and experiences, it's only when something of the future, of God's eschatological imagination, comes forth into the present and invites us to engage with "the power of the future" (moltmann) therein that we discover that our relationships can be expressions of worship to God.
The radical grace of God is in the fact that he, being "the one who loves in freedom" (Karl Barth), chooses to reside with us and be affected by us even though he does not need to. He actually chooses to need us. Grace then, "the supernatural life of God within us that allows us to live our lives the way God would want us to live" (Father Aloysius Ezeonyeka), is the radically separate God opening up to us, allowing us to touch him in present flesh and blood experience. And this experience, the "means of grace," is "an action ordained by God by means of which we wait on God" (John Wesley). God visits us and even in our present experience of God, within our relationships with others and within our interactions with creation, we actively "wait on God" who resides with us in his now-but-not-yet kingdom.