Spar, by Kij Johnson

Marshall Maresca recommended this excellent piece at his blog. It richly deserves all the awards it was nominated for and received. At its core it explores the incommensurability of experience and on top of that, features a truly alien alien, which Gregory Benford described as the holy grail of sf. And (bonus) it avoids the pitfalls of fictions of ideas, because there's something strongly allegorical going on too. Finally, it also avoids the smarmy sense some stories emit of being proud of themselves for being pointlessly shocking, because it's not. That's too much spoilage already, so just read and enjoy. Perhaps not work safe.