The last couple weeks I have read all of the short fiction nominees for the Hugos so I'd be prepared to vote. One thing I discovered is that I either love or hate novellas, and it usually comes down to the ending.
Geoffrey A. Landis delivers the goods with "The Sultan of the Clouds" (Asimov has made a PDF available for free). I initially doubted I'd enjoy the story. I was hoping for a fantasy, partially because my reading tastes seem to run contrary to the genre in which I'm writing, and because the title made me think fantasy as well. Instead, it opened on Mars and I wasn't looking forward to what seemed like it would be a hard science story.
However, although I think it would qualify as hard science, it had a number of steampunk touches and a sense of wonder that was reminiscent of some of the worlds that Dan Simmons created in his Hyperion series. My favorite touch was the idea of kayaking in floating vehicles through Venus's clouds.
This is thought-provoking fiction at its best. Worlds of wonder mixed with an unusual social arrangement (braided marriages) and a mystery lying at the heart of the story. Highly recommended.