This seminar is to Lacanian theory what Badiou calls counter-symbolization is to the rush for symbolization. It regulates the seduction of quick and final interpretations, or of what Lacan has called "After [attending my seminar] you may think you know everything. Don't." It is Lacanian theory's anxiety. And therefore needs to be studied thoroughly, even and especially in its impasses.
The central thesis of Badiou is that Lacan is an anti-philosopher, in that he destroys truth, the thought of the one, and the love of knowledge (and these sound way more trivial than they are). The climax is that Lacan does not, and cannot, offer an answer to "What is to be done" because he is afraid of philosophizing, for only a totalizing discourse could answer that, and such a discourse is philosophical -- and philosophy fills the hole of politics; the hole which Stavrakakis calls "the political itself". But if one looks closely, one can see several categorical blunders in Badiou's commentary, namely regarding the libertine who does not want to wager on an act. Zizek would say the libertine, in rejecting involvement, has already foreclosed his wager; so Badiou very much forecloses the retroactive nature of the act.
In any case, the last session is an amazing dialogue as regards Jean-Claude Milner's "A Search for Clarity", which one is sure to enjoy. This book is to be studied as a counter-balance to the all too giddy Zizeko-Lacanian student, with the stern advice not to give way to his sinthome.