Well, I noticed some night scene graininess in a few spots, but it looked to me more like how the film was shot than any problem with authoring. I checked out one Blu-Ray review after you posted this, and honestly, did not see the flatness or the dirt that reviewer spoke of. I find the overall picture to be appropriately dark.
I look forward to hearing what others think, though. I try to listen to alternate points of views to better help me evaluate what I am looking at in the future.
Thanks for starting the thread.