If you don't have plans to see this movie, you can check the spoilers here and then come back.
I found this to be a decent movie; not great, not awful, just decent. I didn't regret seeing it, probably won't see it again. It had its good parts and its bad parts, as I'll discuss. I feel like that's about as neutral a first impression as I can give, but that's how I felt. I was a bit let down if only because I don't think it came close to measuring up against the 2009 Star Trek reboot; of course with rare exceptions sequels demonstrate diminishing returns, but I had hoped the four-year gap between films meant they really found a way to nail it. The greatest attribute of this franchise to my mind remains the brilliant casting, as there are no duds to be found in the ensemble, with Chris Pine and Zach Quinto as the standouts, plus Zoe Saldana getting a nice chance to step up more here than in the previous installment. Benedict Cumberbatch brought a great sense of command and menace to the antagonist of the piece, channeling Alan Rickman but with more physicality. Alice Eve slotted in nicely as well, holding her own against the aforementioned talents plus Karl Urban, etc. I found Peter Weller a bit over the top in his role, but that feels more down to the plotting than his work (and tough to discuss without hitting spoiler territory). I also think the script was tremendously strong when it came to dialogue; my favorite parts of the movie were the funny moments or emotional exchanges, and that has as much to do with the writing as the acting. It's also a visually stunning piece of work, no question, and the action sequences are top notch, so kudos to J.J. Abrams on that. There were two major negatives dragging in particular the second half down in my opinion, first and foremost being the handling of the story's villain. I feel like Abrams and company got a little too bogged down in trying to create mysteries and twists regarding the bad guy, and in the process muddied the motivations; by three quarters in, I was a bit lost on why certain characters were doing what and whether or not I should be rooting for or against them. My other issue would be what felt like diminishing stakes as the plot rolled out. In the beginning of the movie, I felt like major players were in very real danger, which was exciting, but there were so many close calls early on that by the mid-point I didn't get the sense of any true peril; I know it's tough to really ask for that in an action movie, but for whatever reason, it felt more glaring than usual here, whether it was what felt like a too deliberate "and this is how we'll save whoever needs to be saved later" smoking gun or the "it doesn't matter if people are dying as long as they're not the ones whose names we now" syndrome I've been noticing more and more in this type of film lately. I'd recommend you try this one for yourself, as I think it's very much a case of mileage varying by taste.