I have the 60D and love it. The 70D seems to be a very nice camera - but not a mandatory upgrade for me.
I am concerned about the placement of the stereo microphones on the 70D. It would seem to be that they would be prone to picking up sounds from behind the camera - e.g. the photographer.
The original poster commented in the video about the fact that the USB port has not been upgraded to USB 3.0. I agree this would have been a logical progression.
I also wonder if the touch screen "interacts" with the user's nose when they are looking through the viewfinder.
The built mics can be anywhere on the body. They are omni pattern. They will pick up all round the camera.
Only solution for good audio: mic off camera.
Directional camera top mic better by a baw hair, false economy, not worth the price for most, money better going on an off camera solution.
I don't know the system bus speed of the camera, but going by the video data rates the camera generates, and the speed of current cards, usb 2.0 seems entirely adequate, and will be for some time.
Raise the game yes, but keep it tangible.