This video shows a comparison of the latency between the GoPro HD and a FPV cam. Both scenes are capture by the GoPro HD mounted on the copter. In the left video the TV is showing the picture of a GF-OSC FPV cam and on the right video the picture is coming out of the AV-output of the GoPro HD. You can clearly notice the delay in the right picture.
The GoPro HD Hero has the new firmware v02.05.11 and was in mode r5.