Steve, I had a good look at one of these in a darkened environment and was therefore able to do some proper testing.
I watched some olympic coverage via freeview HD and was surprised to see a fair bit of noise on the picture.
I watched some BMX bikes and some swimming. With the bikes, whenever the bikes moved in the opposite direction to the camera pan, the edges of the bikes and riders blurred. With the swimming, the area around the swimmers (where there was lots of splashing), went blurred and lost definition.
It didn't look like normal interlace mushing, the areas were quite grainy, it looked like dither noise. It was the same on THX cinema and normal, didn't try the pro modes.
I was a bit disappointed with the picture watching sport and anything that wasn't p24.
Did you see anything like the above and was it a freeview HD only issue?