A tipster just dropped off a few internal Microsoft docs that point to a September 8 launch of the Zune HD. In addition to that, the tipster says it's coming in 16GB and 32GB versions. All pretty logical.
We already knew that the HD has Nvidia's Tegra inside, which makes it a high powered, high performance device that can handle HD output and possibly some nice gaming. What we don't know is what the cost of the OLED screen and the cost of Tegra will make the final price. No word on that yet from the tipster.