The console'sAV Multi-Out can output 480i, 480p. 720o, 1080i, or 1080p via composite video, S-video, component video, or HDMI. For audio we have six-channel linear PCM audio over HDMI.
The optical drive slot will play Wii U games that will be on "12cm proprietary high-density optical discs". From what I can tell it's not Blu-ray and it's not DVD. Maybe something inbetween? These discs can hold up to 25GB of data, the same as a single-layer Blu-ray disc. The Wii U will also be able to play Wii games. As for Gamecube support, Nintendo came out with a "no". We can most likely expect an annoucement of GameCube virtual console releases soon. Or perhaps a series of HD Collections.
The controller will have an AC adapter port so that means a rechargable batter and a "sensor strip". Same IR technology as the Wii perhaps? It's probably that dark strip by the camera on the controller.
The Wii U will contain an internal flash memory, no info yet on the size. Storage will be expandable with an SD card or an external hard drive as the console features 4 USB 2.0 ports.
Its CPU is an IBM Power-based multi-core processor as well as a "custom AMD Radeon HD GPU" graphics chip with a "modenr and rich graphics processing core" that will deliver "high-definition graphics support, rich multimedia acceleration and playbackl and multiple display support," that's all the info Nintendo let out for now.
The Wii U might not support the GameCube but it will support all Wii games and accessories, including the Wiimote and Classic Controller.