I spent a while in a Sony store today (amazing unhelpful staff!!) more interested in standing outside and watching the weather than serving customers.
They had a BBC HD preview running on all of the screens bar one that was linked up to a bluray player with some blueray previews on (that stopped and sat on the menu screen for 10 minutes!)
The BBC HD varied in quality wildly, there was a programme with Monty Don in it (looked like some gardening type programme) which was simply stunning on the every size screen, the trailer for the Graham Norton show about choosing a nancy for Olive was full of noise and artifacts on all the screen, including the V/W and X screens so clearly the BBCs HD out put varies widly, I actually think that the Graham Norton stuff was SD upscaled which would make it watchable, if it was an example of HD then it was amazingly poor but was clearly not the TVs but the source material.
I'm hoping to head to another sony store this weeks and see all 3 source types running on the 40 and 46" W's to see what they are like.
The TV world really does seem backwards at the moment, 90% of the tv's are HD and 90% of the content is SD!