The thing that is important to keep in mind is the "look" that the filmmakers were trying to obtain here. The Godfather Trilogy is not a 3D "pop" title, but I am expecting to see detail similar to films in the same format of a similar vintage e.g. The Sting. I am also expecting to see fidelity...
I'm going to take the prudent route and not comment on the quality of this release until I've actually seen it. Based on RAH's involvement and other factors, it's definitely worth checking out.
Screencaps are only as good as the person who captures them. Hardly reliable. I should also note that you're relying on a review without having seen the discs yourself. If you're that concerned, rent the set first.