I think the Kelvin-universe cast is largely pretty good. Zoe Saldana has never struck me as a great fit for Uhura, but I like everyone else, and I think Karl Urban is great. I also like that all the characters get something to do in the movie. The interactions between Spock and Bones, and Scotty and Jaylah are definite highlights for me.
Speaking of, Sofia Boutella's Jaylah character is a lot of fun, and if they actually ever get a fourth one off the ground -- not holding my breath -- I do hope they're able to work the character in.
It's hard to go wrong with Idris Elba in anything, but I do think he was wasted as Krall, who is not particularly compelling, and that's probably the film's biggest failing. But then, I don't think many Trek movie villains are all the compelling. The most relatable threat in all thirteen movies was the giant space probe that just wanted to talk to some whales. 'Cause, y'know...same. After that it's probably General Chang, and then, despite my low regard for the movie overall, Nero.
The set pieces are great. Obviously it's silly, but the opening scene where Kirk gets attacked by the Teenaxi is a lot of fun. The scene where Krall's drones are tearing up the Enterprise is riveting. I love Kirk on the motorcycle during the rescue beam-out scene. And the final fight between Kirk and Krall is really well done, even if the actual threat is kinda lacklustre.
I love the design work. Yorktown station looks great. The Franklin might be my favourite starship design across the franchise. I really like the new uniforms that don't have the textured delta pattern of the previous two films, as well as the Franklin uniform that Spock ends up wearing. I don't love the phasers with their rotating emitter, but other than that aspect they look good.
I recognize that it's pretty much a dumb action movie, but it is, in my opinion, a very watchable dumb action movie. That's really all it's trying to be, which I respect. Am I going to argue that it's technically he best executed movie of the bunch? Of course not! But is it my personal favourite? Yeah. Except for when my mood changes and "The Voyage Home" is my favourite.