Things I liked:
1) Ground combat. That was sorely missing from The Force Awakens. Yeah, we had Finn, Han, and Chewie blowing Stormtroopers away, but since they all have plot armor, it doesn't have the same feel. I wanted to see something like what we saw at the start of TFA with the Stormtroopers, only I wanted to see the Rebels fighting back.
2) That shot of Scarif or whatever the planet is called. After all the dull colors, suddenly seeing this lush green and bright blue planet is eye popping. I love it.
3) Oh snap, are we going to get space combat this time? Please say yes. And please be like Return of the Jedi, where random, no-name Rebels make just as much impact as the heroes.
4) The action overall. This looks like it's going to be a good thrill ride once it gets all the pieces in place.
Things I didn't like:
1) Why did you show Vader? We all knew he was going to be in the movie. He had to be. But they should have saved his reveal for the actual movie. They should have kept his appearances to subtle hints and back-of-the-helmet shots. Keep that mystery air around him until he actually shows up in the movie.
2) Build off of that, Vader seemed to be walking too fast in that scene, like he was in a hurry or something. Vader doesn't move like that. He takes long, menacing strides, not "Sorry I'm late for the meeting, Director," quick strides.