GF 3 starts off like a train wreck. The introductary party is sloppily directed and choppy. Lines are dubbed. Nothing like the introductions in Part I and II.
However, once the deal for Immobliere gets moving, the AC hit occurs, Michael faints, and we get back to Sicily - part III is chugging along at a fast pace, faster than the other ones.
It's ambicious and doesn't make appologies for it's shortcomings and it shouldn't. The opera scene while long, is the most suspenseful part of the trilogy. The first time I watched it I had no idea what would happen and I was on pins and needles the entire time. By then, FFC seems more back in the groove, camera shots are longer and more meaningful, edits are more smooth. We're back in the world of the Corleones. It took some time to get there, but remember, this movie was made 16 years after Part II.
I think most people who hate part III couldn't get past the first 30 mins and never finished it. Such a shame because it really gets better.