Confusing the first time, great the second time Compared to Christopher Nolan's other big movies, Tenet wouldn't rank the highest, but it's still a great film.
The first time I watched it, for the first half of the film I was confused as to what is going on. Then you catch on and I thought I understood the overall story at the end, but still had so many questions and didn't understand the point of many scenes. I decided to rewatch it again, and now I was able to understand it and saw the genius in the story.
My main complaint with this movie, is I wish they went deeper into the lore. Inception for example, brought the idea of going into ones subconscious, and went deep into that idea. They showed how badly it can go wrong, the possibilities that present itself, the good, etc. For this movie about reversing time, they proposed some time travelling theories, but just left it at theories and didn't delve in. Those who watched it may remember when Robert Pattisons character talked about the "Grandpa effect" for example, yet they never attempted it. I would have liked to Christopher Nolan tackling some theories and "what if's" in this movie that he's known for doing in Interstellar, Inception, The Dark Knight, etc.
That was my only complaint. First time watching it, won't be the best watch. Second or third time, you will have a blast. I do think when viewing Christopher Nolan's past films, he goes in deeper and presents a full scope which this film could have benefited more from. Nonetheless, a great film to not be missed!