For me, an important aspect for the mecha genre are the action sequences, and F91 has gorgeous animation with very unique and interesting mech designs. The fighting is fun to watch and doesn't clash with the non-action scenes visually. There aren't many, if any, scenes I recall looking off or grotesque due to little time spent on it.
It stands pretty alone in the Universal Century, the most expansive era in Gundam, so you can watch it without needing to know much of anything about the franchise. That said, it follows the most generic outline for a Gundam story it could have, but the differences are rather interesting for fans of the franchise, and knowing what follows in manga format and was meant to be fleshed out actually makes the movie more entertaining.
This applies to the characters as well - they are fairly generic and knowing about them through close attention to the movie and the rest of the universe fleshes them out more than the movie will.
Being a 50-episode anime turned singular movie (Gundam series tend to be condensed into 3 movies), it obviously has major pacing issues. Little is explained straightforwardly, which while not bad, is very difficult to catch onto when casually watching and is fairly critical since scenes of character development can near instantly turn to the start of action when they felt like they should have been naturally longer. I'd judge this less if it weren't a politically driven movie in-universe, and the politics of the world and reasonings of major characters are very difficult to understand.
The audio effects aren't bad, but for some reason I feel like some of them aren't entirely fitting. The soundtrack, save for a few select songs, is forgettable and generic.
It has some wonderful parts in the animation and a few songs, horrible pacing and development of the characters and the situation in the movie, and is decent in all other regards. It is a movie that is prettier to look at and imagine what it could've been than it is to listen to and understand fully.
