It is probably possible to distinguish between a defense of OOO from an unfair caricature and a defense of OOO proper. I think what you’ve done here is a solid mixture of each. It is a young school of thought, but one which has grown in popularity quite quickly, either because of its skillful use of a particular media ecology (the Internet), or because of its radical intellectual novelty, or both. Personally, I’m not sure how genuinely new OOO is philosophically (I’m partial to tradition, of course; just look at the name of my blog). What I definitely do find novel about it is not so much the employment of its conceptual structure, but the poetics with which it conveys the curves and connections of this structure. It seems to me that Graham Harman is intuiting the same invisible noetic architecture that emboldened ancient philosophers to pronounce upon matters of metaphysical fact. He is seeing what Plato saw and communicating it with a fresh metaphoric fresco: for Plato, the cosmic process involved the extra-cranial and culture-independent participation of ideas in the organization of a formless but living Receptacle; for Harman, the cosmos is the complex and layered perception/causal relation of objects by objects within a sensual ether of elements (where the ether is really just the inside of the inside of the inside of an indefinitely nested series of objects within objects). What is the infinitely hidden identity of an object in itself but an archetypal form or essence existing in an eternity beyond (but still related to, albeit transcendently) space and time? The story is a bit different, but the same characters all seem to be present.
I’m still curious to see how Harman deals with the idea of evolution. Was Teilhard de Chardin right when he suggested that evolution is not merely a theory, but a fact that all other theories would come eventually to adapt themselves to? I’m on page 194 of Harman’s Guerilla Metaphysics, and he just mentioned “time” for the first time. There is a section towards the end of the book where he spends 6 or 7 pages on the issue, and I know he actually does want to preserve change (at least phenomenally), but it doesn’t seem as though there will be any mention of evolution (change with direction/s). My guess is he doesn’t think evolution is all that relevant to metaphysics and ontology. Teilhard would strongly disagree. I am not sure if Harman’s ultimate word on reality (that it is turtles, or objects, all the way down) does justice to our intuitions (and perhaps the intuitions of other organisms/objects) that the universe with its multiplicity of objects is not simply Being, but striving to become something more.