The TL;DR is that it's so good, it increased my time on Reddit by 10x or more versus using the website. I had to delete it because it was such a joy to use, it's all I wanted to spend my free time on.

More specifically, just a few things: 1) lovely UI design with proper adherence to iOS human interface guidelines, 2) useful customization, 3) flawless performance throughout, 4) gesture support which translates into being able to sift through a lot of content and conversations, 5) complex native (performant!) in-app support for many media types hosted on all types of 3rd party sites, 6) and just all around thoughtful and thorough support for the entire Reddit platform and its features.

All of this executed extremely well by just one person. Frankly, an inspiration and should be championed here.