EDIT:
A bit over a month later and I've decided to rewatch this movie as I'm on a bit of a Kyo Ani binge right now, and I'm enjoying it a lot! I've certainly found a new appreciation for the studio and their work, and I felt like this review was deserving of a little bit of a touch-up. I will not edit the original review itself as I believe it's worth keeping as-is to represent what someone less familiar with Kyoto Animation's works would see this as. Here's some things I've changed my mind on:

• The animation quality certainly isn't "average". While not on par with some of the more recent Kyoto Animation works, and even Hibike! Euphonium looking a bit smoother, it's still far above average and high-quality.
• Kyoto Animation's original music is fantastic. While still not something I would listen to the OST of casually, Kyoto Animation has a knack for making distinctly simple music that feels like it would fit better to the scenes than anything more complex or traditional. It makes the touching scenes even more emotional and I certainly appreciated the musical aspects more the second time around.
• It made me cry this time :(

Was initially very uninterested in this, as the concept didn't really hook me in. Had an evening to kill relaxing and decided to give it a watch, as it seems to have plenty of praise. Such an emotional roller coaster. Didn't make me cry, but definitely got me feeling and moistened the eyes.

I haven't read the manga, but Koe no Katachi definitely seems like something that would shine best in the manga format. As a movie, it's not half bad, and it's about the best it could be in a non-manga format. The movie format maintains very solid momentum that would be lost as an anime series at the sacrifice of fleshing out side characters and amount of content. However, nothing about Koe no Katachi as a movie is particularly "bad". Someone who's read the manga would know more about this comparison than I.

The story is unique and very well written, certainly a tearjerker from start to finish, whether from sadness or happiness. Movies, anime or otherwise, tend to leave me bored at times, but Koe no Katachi was a refreshing outlier. I can't commend everyone involved in making this movie enough for simply maintaining momentum and keeping me interested for a solid two hours. The storyline is also very coherent, no forced twists or time jumps that would simply leave viewers confused. It feels like every film does this nowadays, so it was very refreshing to just have a normal, well-written timeline.

The characters of Koe no Katachi feel realistic and lively. Almost everyone has traits that reminded me of either myself or people I know. Most everyone who's old enough to have gone through high school will find at least a few characters very relatable. This is probably the most hard-hitting emotional aspect of the movie, and it's executed very well. Could easily get me crying if it caught me int he right mindset.
There is some controversy regarding the story's focus on a disabled character, but the people who view this as controversial are the same people who want to see more disabled/minority characters in media for equality's sake. Personally, I believe the disabled character in Koe no Katachi is certainly not representative of all deaf people, and you'd be foolish to believe otherwise. This is a fictional character in a piece of media ultimately meant to entertain viewers. Of course there's a life lesson to be learned about treating people with kindness and overcoming your past mistakes through bettering yourself, but media like anime or movies don't become popular if they aren't enjoyable. Writers shouldn't limit their potential on what a handful of people would consider offensive.

That said, here are some things that are better suited as a bullet-point list than single sentence paragraphs:

• The art is fantastic. Clean and memorable style with detailed backgrounds. Animation is about average for anime, but facial expressions were particularly well-made.
• Sound rating can be a bit confusing with some anime, I'm never sure if I'm supposed to rate it on music or actual sound quality. As for Koe no Katachi, nothing about the music stood out to me, but I guess it did what it needed to do decently, if a bit generically. Music aside, the actual sound quality is great. Sounds such as passing traffic actually had me glancing out my window to see if what I was hearing was from the movie or real life.

Overall, I liked it. It's not the best thing since sliced bread and it didn't change my life, but it's the first movie I've enjoyed for reasons other than realistic and high-adrenaline action in a long time. Its quality is a bit over-exaggerated as is most everything on the internet, but Koe no Katachi certainly isn't bad.