I've only read
Uprooted, which I just finished on Sunday morning before I saw the results. I didn't really think it was up there with the greats, even though it has already won a couple of other awards. I was still sort of hoping it would win, since I've read every best novel winner to date, and it would have been nice not to have to go out of my way to read this year's.
Edit: I guess I also need to read the Retro Hugo winner,
Slan by AE Van Vogt.