An article I found over at TrustedReviews shows pics of an Xbox 360 that was apparently spotted at IDF, on the third floor of the Moscone Center. This particular Xbox 360 was part of a Microsoft Media Center demonstration, and was being used as a Media Center extended device, streaming all its content from a Media Center PC that was situated close by.
The video that was being streamed was 720p HD content, but Microsoft assured me that the 360 will be capable of showing 1080 HD content for the ultimate High Definition experience.
The Xbox 360 was hooked up to a Samsung DLP rear projection TV via component video. It's a shame that it wasn't connected via HDMI, but the Microsoft representative assured me that the 360 can output over HDMI, but that there isn't a cable available at present.