Just watched this in the theater today. TL;DR, this was a very well-animated idol anime with great songs for a more mature audience (compared to, for example, Love Live or IdolM@ster). Its small flaws come from the fact that it is adapted from a novel, so its running time feels unsatisfying for getting to know the characters, and the drama ramps up very quickly in the second half of the movie then gets resolved relatively conveniently.
Overall score: 8/10
Animation: 9/10. There was some spotty CGI but for the most part everything was very well done, and certain scenes were downright impressive with the way the characters moved.
Sound: 10/10. The songs were very enjoyable and I wouldn't be surprised if this turns out to be one of those movies where the songs outstay the movie in popular consciousness years from now.
Characters: 8/10. Unlike your typical idol anime where all the girls are happy-go-lucky with their minds set on idoling, the girls in this one each have their motivations and flaws which become apparent in the second half. These girls feel a bit more realistic than your typical idol anime heroines, which some people will like and some will not. I found all 4 of the main girls likeable by the end despite the drama.
Story: 7/10. Similar to my comment about the characters, this is a much more dramatic take on being an idol than your average idol anime where everything is rainbows and sunshine. The girls have conflict and struggles with a few touching scenes that will make you root for them, but not everyone will enjoy that aspect. Pacing also feels very quick in the second half compared to the buildup of the first. Not a huge issue though.
In summary, this was a very solid and satisfying "I'm glad I watched that" movie with more mature drama than your typical idol anime, but I am not sure if I will be rewatching or remembering the details in a few months.
Recommended anime: Wake Up Girls! is another idol anime with a slightly more "realistic" take on the industry and the struggles of being an idol. For a more lighthearted comedy about upstart idols, I highly recommend "Oshi ga Budoukan Ittekuretara Shinu."