I watched the movie when it first premiered in Anime Expo and am giving my honest feedback.
Despite being plastered with subtitle "EVOLUTION", the origin story that was originally in the Japanese director's cut version of the movie is removed, which I found to be a huge disservice done to Mewtwo's character arc. This was honestly my biggest gripe, especially since this movie was pretty much advertised as an "enhanced-version" over the original.
ff you are expecting a shot for shot remake of the first movie then that is what you will more or less be receiving. There are a few added scenes here and there but they don't really contribute anything new to the overall story.
On a positive note, I found the animation and art style to be very gorgeous. You can tell they put a lot of effort into making the CG looks superb. The film's trailers does not do the actual film justice in the artistic department.
So while the film is appealing to the eye, I still found the story to be woefully disappointing due to unnecessary cuts over additions that could have fleshed out the story. If you are looking for a complete narrative that includes Mewtwo's integral origin story, I recommend watching the Kazenban-version of the 2D film.
Overall, I found this film to be a far cry of an "evolution" and it really just didn't do it for me.