Will 720p60 GOP12 have artifact issues?
 

Will the few image issues with the 720p24 GOP6 be exasperated in the new format. Has anyone had access to a camera to test?

It only uses the longer GOP for 720/60p

The HD200/250 functions exactly like the HD100 for all the lesser settings. This is done to maintain compatability.

We'll all have to wait and see, however, mathmatically 12 GOP of 60fps is the same fraction of time as 6 GOP of 30fps (1/5 of a second). It seems to me that if there are motion estimation errors in the 60fps, they would not be noticeable. As far as the encoder, JVC makes top of the line mpeg encoders so I can imagine the camera will be spectacular as the HD-100 is.