Regarding Laura Dern's character... Yes, Poe's mutiny could have been avoided if she had just explained her plan, but I just took it to be a flaw of the character. That she was a stuck-up jerk and just didn't like Poe because of his recklessness in the opening battle.
I was kind of hoping the code-breaker Finn and Rose find on the casino planet would be Lando Calrissian. But, I don't think that whole subplot was completely useless. They did meet up with that force-sensitive child, gave him the ring, and now he has a glimmer of hope. I felt that was nice way to end the movie.
Kylo Ren killing Snoke and then setting himself up as the new supreme leader was a nice twist. And General Hux wrestling with him for the position. Some interesting possibilities there.
Luke becoming a Force Ghost has some interesting possibilities, too. I wonder if we'll have a Force Ghost reunion in Episode IX. Obi-Wan, Yoda, Anakin, and Luke.
![Very Happy :D](./images/smilies/icon_biggrin.gif)