I don't like this caching refaddr() inside the object. One of the purposes of inside-out is airtight encapsulation and although I don't see straight off how this can break that, it smells funny to me. Nor do I see the good use of it; why not just use refaddr() as usual?

While I applaud novel approaches in general, my appreciation is inversely related to scope. When you reach the level of a whole scheme or concept for all classes, you come to a point where I expect any novelty to come with a great reward. I'm not even sure that inside-out pays out sufficiently, considering that so many old classes are HoH-based.