There was actually quite a bit of digital alterations: I counted at least two instances of set lights removed, Baja was removed from the horizon in a few short scenes, stars were added to numerous night time scenes, including one with the corrected star field for 1912, one instance of obvious flexing foam set as a passenger crashed into has been fixed, etc. (Jack's window reflection and partially visible unfinished Titanic set remain unfortunately).
I know a lot of people are not big fans of teal/orange color grading, but apart from that, this is a tremendous 4K restoration job. As good as I have EVER seen. The detail is extraordinary, with very little present grain. Just marvelous.
This will be one of my favorite reference discs for years to come. It's a must own for any Blu-Ray collector.