I found an interesting conversation between Protevi, DeLanda and Thanem about Deleuze. They also discuss the “science wars” and how philosophy is an interdisciplinary meta-endeavor, but I'll leave you to read that on your own. Here are some excerpts relevant to OOO, the last of particular interest to you mereological non-assholonians.
Deleuze’s main contribution to philosophy, it seems to me, is to have rescued realism (as an ontological stance) from the oblivion in which it has been for a century or more. In some philosophical circles to say that the world exists independently of our minds is tantamount to a capital crime. Non-realist philosophers (from positivists to phenomenologists) have created a straw man to kick around: the naive realist, who thinks we have unmediated access to the external world and who holds a correspondence theory of truth. So the key move here was to create a viable alternative form of realism to deprive non-realists of that easy way out. Similarly, when it comes to defend the autonomy of non-human entities (atoms, molecules, cells, species) the crucial manoeuvre is to account for their mind-independent identity without bringing essences into the picture.... The identity of any real entity must be accounted for by a process, the process that produced that entity.
I cannot imagine a materialist philosophy which is not also realist. On the other hand, someone who believes that god and the devil exist independently of our minds is also a realist but clearly not a materialist. The only problem with the term 'materialism' is that not only matter but also energy and
physical information are needed to account for self-organizing phenomena and the processes which fabricate physical entities. Also, some forms of materialism may imply reductionism (of the mind to matter, for example) and that is not at all implied by the term 'realism.'
I’d certainly agree that fitting materialism into the contrast of realism and idealism is important. I’d also say that while materialism is often contrasted with idealism, you could also say that the foil for Deleuze and Guattari’s materialism is dualism, specifically a spiritualist dualism. So their materialism is a monism (another way of putting this is to say they demand immanence rather than transcendence). Spiritualist dualisms have, because of an impoverished concept of matter as chaotic or passive, too hastily had recourse to a 'hylomorphic' schema in which an organized transcendent agent is responsible for all production. The problem is how to account for the ordered and creative nature of bodies and assemblages, for if matter is chaotic, it can’t account for order, but if it’s passive, it can’t account for creativity. Deleuze and Guattari’s materialism avoids the forced choice of matter’s chaos or spirit’s
transcendent ordering by calling attention to the self-ordering potentials of matter itself, as outlined in the researches of complexity theory (as Manuel point out above, you have expand the sense of 'matter' to include the energy and information of 'material systems'). Deleuze and Guattari can thus account for
order and creativity in the world without the heavy ontological price of a dualism or the unacceptable phenomenal price of the denial of creativity as illusory, as in 'God’s eye view' spiritualist transcendent determinism.
In this ontology all that exists in the actual world is singular individual entities (individual atoms, cells, organisms, persons, organizations, cities and so on) whose main difference from each other is spatio-temporal scale. There are no totalities, such as 'society as a whole,' but a nested set of singular (unique, historically contingent) beings nested within one another like a Russian Doll. Between one entity and the larger one the relationship is one of parts to whole (not one of membership in a general category). This link is machine-like: lower scale entities form the working parts of a larger scale whole, a whole which emerges (and needs to be continuously maintained) by the interactions between the parts. Thus, interacting persons yield institutional organizations; interacting organizations yield cities; interacting cities organize the space in which nation states emerge and so on. This changes the very way in which the problem of agency and structure is posed, since the term 'structure' illegitimately conflates several scales and deprives organizations and cities of causal agency.