Jack, exactly! What happens when the church doesn't "work"? Unfortunately, I think that's often the case, and is probably at the root of why many people walk away from church and don't look back. And coming to an understanding and acceptance of the diversity within the church—the many different types of people—is key, as you eloquently pointed out: "How does church really act as a group with fluid boundaries, made up of people in all stages of brokenness, of different ages, classes, races and all the other categories?" (Actually, I think that idea fits in well with my post about the imperfect Golden Rule, too.) 

But I'm curious about your last question, because I honestly believe that when we gather, in all our imperfectness, God *does* show up. We just aren't open to him—we don't want to hear what he's saying, or change in the ways he's nudging us to change. When we feel like we've "got nuthin," then I think we need to make a radical paradigm shift of some sort, to shake things up force them out of our complacent rut. Easier said than done, I know.