I quite enjoyed it, actually. I was expecting it to be dire, but it's actually a perfectly decent Terra Formars adaptation. Of course it's still Terra Formars and so it's basically a waste of time, but it's no worse than the anime and it could even be said to have a few sparks of life.
Plot summary! Mankind is going to Mars (again). 500 years ago, we went there to terraform the place and we left behind some cockroaches. Now, it's time for pest control. Unfortunately the cockroaches have evolved into seven foot tall bipeds with super-speed, flight and a strong desire to kill humans. How would you react if you saw a cockroach in your kitchen? It seems to be the same with them, but in reverse.
The big question was of course the director. Which Miike was going to show up? I love his films, but I got burned with Yatterman and Ninja Kids. Both of those are based on famous anime/manga, but they're also children's films. This is ultra-violent neo-military SF where the heroes die like flies. That sounds like a better fit for him, although admittedly the results are a bit tamer than I'd expected. There's almost no gore, with the splatter being white instead of red. (They're insects. Real insects actually have yellow or green blood, believe it or not.) However Miike's comfortable with the cartoonishness, even introducing a silly villain back on Earth who's out-camping anything on Mars. This film has:
(a) manga-authentic cockroaches. They look exactly right. No one's had a "this is silly" cringe, which means that their goofiness actually looks good.
(b) really daft visuals when it comes to the humans' insect superpowers. Again, this is true to the manga. Miike's putting the original on screen, with no judgement or filters. I still find it dull as a narrative direction, but there's no way around that if you're adapting Terra Formars.
(c) Shun Oguri's villain, who's basically Gary Oldman from The Fifth Element. (The hairstyle's more restrained, but the performance is more affected.) He was cool. Bonkers, but cool. Some bold choices went into that character, especially since I don't remember him from the anime and so the filmmakers presumably had a completely free hand in how they portrayed him. (In fact there's someone of the same name in the manga, but with a much less prominent story role. The film's version of him is basically a replacement for all those politicians.)
(d) the tsunamis, which I enjoyed.
The biggest change is the soldiers' uniforms. They're not dressed like Aoshi from Rurouni Kenshin, but instead as Star Wars stormtroopers with no helmets. (I now know that Star Wars would be better if it had female stormtroopers with figure-flattering breastplates.)
The script's adapting the Bugs 2 arc (i.e. manga vol.1 and the two OVA episodes) rather than the Annex I arc (i.e. manga vol.2+ and the 13-episode 2014 series) or anything else. Sounds sensible to me. Tell a story that belongs at that length. Admittedly it's no more interesting than any other bit of Terra Formars and the film falls flat with the only scene I like in it ("talk to it"), but at least you won't have to start out by hitting the script with sticks. They've cut most of the flashbacks (good) but they're also not spending too much time on character establishment and build-up at the beginning (hurm). I'm not sure that the film's got all of its story logic straight, e.g. did these people know what their bug superpowers were in advance or not?
As for the acting, it's fine. Hideaki Itou has one reaction shot so poor that I could only take it as an unusual character choice, but he's mostly fine and he has a splendid hero face. The rest of the cast do respectably with what little they're given. It's silly-but-hard-bitten SF nonsense in which very few actors get much beyond the odd line here and here. The female characters get "blink and you'll miss it" roles and not enough screen time, but that's not due to sexism. Their male co-stars are getting the same. All things considered, everyone comes across fairly well.
It's a fair adaption, I think. It's no better than the unremarkable anime, but it's not embarrassed about what it is. (I've heard that the manga's been quite successful, but I'm not planning to buy it and verify that for myself.) It's not afraid to be nonsense when the story demands it. It's a pretty convincing "spaceships and soldiers" future. It even has what might have been a sequel-hunting ending, although, ahahaha, no. Watch this if you're in the mood for yet another forgettable film that owes its entire genre to Aliens, but is also sillier.