According to XCM it will also be able to output 1080i, as the cable converts the analog signal to a digital signal, which is why it can't do 1080p. It's also got a pair of RCA stereo audio outputs and an HDMI to DVI adapter.

The cable is apparently scheduled to go on sale in the middle of September, which means it's only a couple of weeks away. It's not going to make your old Xbox 360 as good as one of the new HDMI equipped ones, but it will at least allow you to connect your old Xbox 360 to an HD TV via HDMI.
You can check out a couple of additional pictures here

