My overall impression is positive. Part of the hype for this was blurbs saying this is the "best Transformers movie", but that's... As low a bar as it gets. It's not particularly mind-blowing it memorable just yet, but it is very good.
Visually I'm not super into the models and faces. Most of them have this odd wasp waist thing with wide rectangular torso halves. But when they don't (Bee, Elita, Seekers) the models look great. The faces are also not really my cup of tea, but they're serviceable. Everyone does have a distinct face structure (Sentinel's is very wide, Megatron has a nice lean angular cheek to chin) which is a nice characterization thing. It's nice seeing the distinctiveness of each model look through each upgrade (miner, with cog, powered up by Matrix/Megatronus cog), although multiple reformats kind of wears the device a bit thin.
Beyond that, though, this Cybertron is gorgeous. Love the wildness of the surface and the sheer kid magic of trains and transports on self-extending roads and tracks to who knows where. Some of the altmodes are particularly neat (I MUST have a Studio Series Airachnid, and I hope a beefier and more detailed Studio Series Alpha Trion is due too).
The music is by Brian Tyler and is nice, with some bits actually weaving the transformation sound into them (at least once, at the High Guard hideout). The continuous hopeful bits while Orion falls into Cybertron are nice. The requisite "pop song we didn't use in the movie" that plays over the credits is "If I Fall", which is not very good.
The voice acting is a mixed bag. It's the most emotive I've ever heard Scarjo, and I like her Elita. Brian Tyree Henry is great, just great, as D-16/Megatron. Jon Hamm does the smarmy politician voice very well with Sentinel Prime, although I could have done with a bit more of an edge when the character's shift is done. Keegan-Michael Key's B-127 is... Okay. Idk how I feel about Bee being this motormouth comedy machine (Badassatron was one of the weakest jokes in the trailer, and sadly but unsurprisingly it's a runner), but it doesn't take over the storytelling and he's good at it in any case. Buscemi is PERFECT for Starscream, and I love that they worked in a momentarily screechy voice glitch. He's one of my favorites in the whole thing, just above Fishburne as Alpha Trion.
Finally, Hemsworth as Orion Pax/Optimus Prime... is kind of what I expected from the trailers. It's a serviceable performance, and Hemsworth's strength of good comic timing and banter is great for a looser, young, pre-leader figure OP. But so much of his effort seems to be going into suprressing his accent, making his words rhotic (if with a bit of a lisp sometimes), that the acting kind of falls a bit flat. Not that the script gives him as much to act with as Brian. For instance, the speech he gives to the miners feels like it loses steam halfway through; allthough the scene is trying to sell us on how inspirational he is now that he's grown into the role, after the borrowed line from Alpha Trion he feels like he's trying to get through it. (The big closing speech, which I liked that the movie had, was undercut by how he kept saying Autobots as Auto-Bots. Like yes, I get it, auto- as in autonomous, you said.) I almost would have preferred that he just keep his accent if it let him speak more naturally, because this was a bit wooden (and not in a good way).
That said, for the most part the characterization is great. B-127 is kind of automatically the weakest here as he's basically pigeonholed into being the punchline machine, although ciphers like Soundwave and Shockwave get much less for now. Elita is established very well as a bot with her own aspirations and standards, an equal to the others. Everyone gets some good lines, and occasionally there are some extra good bits ("You have neither the touch nor the power").
The bond between Orion and D-16 is palpable and believable, although the progression of each character is a bit clunkily done. Everything after the cave and the reveal about the Primes has the right pieces (Orion believing the truth will free the people, D swearing a murderous revenge and swearing off leaders, then leaning into the "might makes right" credo of the High Guard) but could have been done better. Part of this is complicated by how compsct the timeline of events seems to be. These big sweeping character alignment shifts would benefit from time for reflection or resentment to go to work.
Love the way the movie plays with the lore bits it needs for the story. Starscream and the High Guard going off on their own is a nice twist on "the Decepticons are the military hardware kind", and them hiding out in the surface and plotting against Sentinel is interesting enough that they should get their own miniseries.
The 13 were well used here, with an interesting new take. It was surprisingly thrilling seeing Vector Prime on the big screen, basically looking as we know him. Still rolling my eyes at the continued use of "Megatronus" (FFS, just call him Megatron) but giving him the Tarn look of having the Decepticon sigil for a face/mask is a great move. Can't recall if it's been done, don't care. It's good here. I like that this uses Zeta as the 13th, neatly avoiding any Arisen nonsense, although it's interesting that the 13th is essentially the Matrix Bearer, so any inheritor is kiiiind of like the Arisen, but at least that's not explicitly a thing. Loved the designs for the most part (seeing them all in the group shot bracing for the betrayal was cool), but reusing dead 13 member t-cogs was a bit awkward. The whole timeline of the 13 essentially not being THAT ancient (50 cycles?) is certainly something to think about.
The new story working of Sentinel selling out the race to the Quintessons, and the Quintessons continuing to be in power, is a bold move I really like. I do wish the Quintessons looked more like the Quintessons of old, but that's a minor concern. When Sentinel and his guard bent the knee I was as taken aback as the characters were. Sentinel having betrayed the Primes, and going on to tamper with newborns to dictate their destinies, is a deliciously evil thing to give to a character, and would have been nice to really explore if not for the kid movie of it all.
The big fight at the end was... Interesting if weird. Big frenzied shootout, great use of space in aerial combat blocking. Elita chasing down Airachnid was a great sequence. Crashing the train was great, miners flying in for the rescue was a good, well-paced development. Etc. The combat in general is great, mixing typical punchy punchy with more dynamic and inventive melee spots (Prime ripping off Megs turret and hitting him with it, only for it to... Transform back into part of Megs' body, I think).
But the killing of Sentinel lost something in being intercut with Orion being given the Matrix. Threw the pacing off by a lot, and the rest felt a bit repetitive because we'd already seen both get upgraded and get physical.
Even Megs letting Orion fall after taking the shot was a little thin by itself as a character beat. "I'm done saving you" works as a callback/twist on all the saving they'd done for each other, but a line about not saving someone who was only in danger because of protecting a liar and traitor would've added some substance to that.
And the ending was... I'm not sure I get it. It seems like it would've made more sense for Optimus to offer to work together to rebuild, or for Megatron to lead the High Guard and protect Cybertron, and for Megs to soundly reject that because he'll put up with no more leaders, and no more corruption and deception. Instead it's "I cut your cannon, get out." (And then as soon as they leave, the Autobots turn the Energon back on.)
The big closing speech... Are the Quintessons not just hovering above Cybertron constantly? Are the Autobots not going to take the battle to them? Or are they waiting for the Quintessons to return and then fight them into leaving for good?
Anyway, a very good bit of Transformers media with nice lore play and worldbuilding. I particularly love the twist that the constantly-transforming surface of Cybertron is now where the secrets are, rather than the core, which is now more the world they know (although the Matrix still being "there" is okay too). Way more cameos and existing designs and names thrown in there than a single viewing can parse out (I kinda marked out at Cordon on the leaderboard for the Iacon 5000). There's what, only a handful of new names and designs here -- Behemoth and one other racer I didn't catch, the name Darkwing given to the big angry boss guy) -- and almost every shot has someone or four you'll recognize.
Already making plans to see it again.