It's pretty good. I enjoyed it and I'd recommend it. I prefer the anime version of this story, which goes into more detail, but on that argument I should be championing the original manga (2008-17) above both adaptations.
They're also different enough that it's worth watching both. The most important variations, I think, are:
(a) the film covers less ground, which is sensible given the differing run times. (103 minutes vs. 13 episodes.) They feel very similar all the way up to the return of Yamato's old friend Kai, but Megumi has become practically a walk-on role. We get a cursory glance at the story arc about Yamato becoming a model, but almost no attention is given to Megumi and, frankly, by that point the film's dashing for the end credits.
If I'd been the actress cast to play Megumi, I'd have been thrilled. It's a fascinating, fucked-up and multi-layered role... in the anime. In the film, she's a pretty face who gets a few lines of dialogue. (She's played by a real model who was making her acting debut, but the role's so underwritten that this doesn't matter and I'd never have guessed if I hadn't just looked it up.)
(b) the film's version of Mei isn't inviting a diagnosis. You wouldn't use words like "syndrome" and "disorder" when discussing her. She's comparatively normal, really. The character still works well in the story and made me laugh, but she comes across more as a normal person who'd fallen into a negative pattern of thinking. She's also the prettiest girl in the film (as per the iron law of cinema, which is doubly true in Japan), which unfortunately means there are characterisation beats you can't do with this version of her. When anime-Mei felt inadequate alongside professional models, you understood. This one, though, has nothing to worry about.
(c) Tasuku Nagase (who plays Kenji Nakanishi) looks about 40. Ironically, he's baby-faced in lots of his official photos (e.g. from when he was in Kamen Rider), but I didn't believe for a moment that this person could still be in school.
The similarities are much more striking than the differences, though. Until Megumi appeared, the two adaptations of this story felt the same. There were some minor rearrangements. We're not shown the rabbit incident up front, Mei and Yamato going home together isn't as big a deal and I was disappointed not to see Kai's endearing geek enthusiasm for "Land". Overall, though, I was impressed by how much ground the film covered without feeling compressed. It didn't feel rushed. It unfolds nicely, feels natural and works very well.
I like the cast. Haruna Kawaguchi does very well as Mei, despite arguably being too tall and too pretty, and I enjoyed watching her. I was also pleasantly surprised by the film's other casting choices. The cast don't look like boy band androids (which certainly can't be said of all Japanese live-action film and TV). It's not like watching a shampoo commercial. Rika Adachi is terrifying as Aiko. The boys are capable of looking sort of ugly, in a likeable way. They're a lively, distinctive-looking bunch and always fun to watch.
It's a good film. I think it tails off at the end, having found/constructed an adequate point to stop instead of actually having a climax, but even those scenes were still okay. Most of the film, though, is engaging, funny and surprisingly faithful to the original work. It's way above average for the category of "Japanese live-action films based on a manga that also has an anime TV series".