You sure you got the disk up where you're watching the HD version and not the SD version? Not to be-little you or anything, but I've done that myself with these stupid "combo" disks. Twice now...watched the hole freakin movie thinking, hu...that ain't too hot. Then figured out I watched the SD version.
If you have, then something is weird. While the Oppo does a darn fine job, I've popped an SD disk in the Oppo, and an HD disk of the same movie in the A2 and the difference has been startling, every time....