The short of it: I enjoyed it a lot. The animation, particularly of Nimona and her emotions, is incredible. Perhaps my only complaint about the animation is it sometimes seems as though the titular character is animated in a separate engine and composited in. Particularly when she takes the form of pink animals, though it could just be an effect of her bright colouring against the pale backgrounds of the dystopian walled city, she looks pasted in. It could be partly due to the intended stylistic effect of making 3D film look like a comic, but it distracted me. A lot. I’m the only one I know who watched the film and noticed it, however.
The dialogue took every opportunity it could to crack jokes, and was rarely overly expository. It was a lot of fun, especially Nimona’s lines, which dripped with personality. I think some of the other characters, while they had more obvious development arcs, were much flatter. In fact I’d go so far to say that the biggest failure of writing in the film is that Nimona is not the main character. Yes, despite the title, the film is written primarily from Ballister’s perspective and focuses primarily on Ballister’s plot. In the scheme of things, his concerns seem superficial in the context of the story, save for where they directly impact Nimona’s.
In regards to the story, I’ll also say, it rests on two tropes, and I won’t spoil the second even though it’s obvious from the trailer, from the inciting incident five minutes in, etc, but the first is this: people are different but that’s no reason to be mean to them. This has been a common theme in animated films going at least back to Shrek, probably longer, but the deluge of them over the last two decades has been quite tiring. Admittedly animation lends well as a medium to this kind of story, and America’s reluctance to accept animation as a medium for any but family-friendly storylines increases the likelihood such will be greenlit as marketable, but gorrammit I want me some IP that isn’t obsessed with proving to its internal universe the characters are worth a damn.