I'm considering using an accurate 35mm grain plate (5-or-so seconds long, on loop) in softlight-overlay to mask the macroblocking I see here and there.
The macroblocking, surprisingly, isn't bad on this version of The Matrix (the open matte 1080i HDTVrip), but it looks so much better with the 35mm grain plate. It hides the small bit of macroblocking really well.