Thought I'd throw my nickels worth in here;
I guess I still kind of wonder what exactly it is? I have a 971H and don't see any problems so far with all the movies I have tried with "blocks". But then again, I don't know exactly what to look for, so maybe ignorance is bliss?
What IS odd to me however, the DVD player the Oppo replaced (a 3-4 year old Toshiba SD-3800 I belive) had some weird anomolies similar to what people say macroblocking looks like. As an example, in U-571, when the movie first starts, it kind of zoom's out of the German Captains eye. On my old Toshiba the center of his eye (forgot what its called....the black part anyway) was actually divided up into 4 big blocks of differing shades of black. It never bothered me, but I noticed it.
Now that I have my Oppo, and things are calibrated, it doesn't do that anymore...Odd.