I think Guattari Hero's question about the convergences, or lack thereof, between Derrida and Lyotard gets at the heart of a meta-level tension that runs through much postmodern/poststructural theory. Namely, are the developments that characterize postmodernity representative of a rupture unique to that (this?) period, or, rather, have such "developments" always "been the case," and we are just now coming to realize their validity/utility? There is probably a techinical name for this distinction; in fact, it might be postmodernism v. poststructuralism. We should ask Professor Fitzpatrick.
In any case, I think Derrida comes down on "discovery" side of this dichotomy. His formal analysis of the inherent aporia of structurality does not suggest that at some point in history structures were "more centered" or "more center-able." Lyotard, on the other hand, appears to situate postmodernity along the same linear trajectory as pre-modernity and modernity. The Derridean positions makes more sense to me. Indeed, I wonder if Lyotard isn't doing a kind of violence to the "project" of certain critical theory by contextualizing it according to this narrow conception of historicity. For instance, in the shorter essay, he claims that avant-garde artists are reacting to previous artistic movements - do we have to understand them in this way? Is life - art, literature, theory, everything - reducible to this kind of reactive dialectical materialism?
Another question: I was rather mystified by Lyotard's claim that "work can become modern only if it is first postmodern" (79). What did you you make of it?