GPGPU basically means that the GPU will also do the job of the CPU. Maybe the Wii U won't have a CPU at all, or the GPU might just be assisting the CPU (which means they can afford to put a lousier CPU in there).
When the volume on the video is maxed, the audio is distorted. If I decrease the volume on the player and increase it on my system, the audio is fine even at very high volumes, so it doesn't seem to be a problem with my speakers or earphones.
Video played with Progress, High quality setting, on Google Chrome 20.0.1132.57