I was with it, more or less, until the end. I'm not sure I read it as "preachy", though I can understand why others did. Instead, I felt it was simply a stretch. For me, that final epiphany to surrender came out of nowhere, and felt very out of character. Bryer wasn't concerned about the politics until that last couple paragraphs, and he certainly wasn't tired of running or breaking the law(s). The more the narration elaborated on the reasons for Bryer's surrender, the more I felt like I was listening to the end of some other character's story.
Also, the politics of the planet felt tacked on -- the politics and inter-special tensions were told-not-shown, and as a result, the stakes felt very abstract, especially when compared to the very tangible action, which I did enjoy. It seemed like the story could be stronger, more visceral, personal, and disturbing without the political angle. That, or the politics and tension could take a step into the foreground, and permeate the piece, as in a story like "The Sundial Brigade".
Really enjoyed the planetary and xenomorphic descriptions, though. And reading was quite good.