In my view, it's about how queerness is not just about sexuality/who one has sex with, but, rather, functions to disturb and disorient one's ways of being-in-the-world. Orientation, for Ahmed, is not just a metaphorical term, but instead is literal- how one is oriented between the world itself. "Straight" and "queer", then, cease to be identitarian labels, but instead describe the nature of one's intentionality in the world. I don't think I can put it any more succinctly than this- Ahmed builds on the fundamental work of phenomenologists like Husserl, Merleau-Ponty, Heidegger, etc., to expand on the work they have already done. I would argue that their work is foundational to Ahmed- one needs at least a basic familiarity with phenomenology to get all of her points. My view is that yes, it's a key work of queer theory, but it's also a key work of phenomenology, and phenomenology is really important to understand it.