Ahhh, the Twitch app. With Microsoft pushing its own service for streaming gameplay, it's hard to imagine that Twitch would be allowed an app that actually has decent features and works well. However, that seems to be what you get.
Keep in mind that this app is completely free, and I am reviewing it as such. Anything that is free is going to have an easier time getting a decent score than something you have to pay money for.
The overall experience of the app is very pleasant. Nearly every feature from the website as accessed from a browser is there, and mostly easy to use. You have the ability to watch anything you'd like (with many different search options) and stream whatever you're playing directly from your Xbox One. The search options for Xbox One games are particularly incredible, allowing you to search for gamers who meet certain criteria in game statistics. Want to watch the Killer Instinct player currently streaming that has the highest win percentage? No problem. On top of all this, the app is responsive and rarely hiccups in the way that users of the YouTube app are used to.
The app is optimized for regular use and set up so that you pretty much never need to log on using any other device. As long as your internet connection is stable, streaming is smooth, and thanks to Xbox tracking your gaming statistics, you are pretty likely to get views from people using the Xbox One app if you have good stats in the game you are streaming. In other words, all you have to do to get views is be good at a game... even if you've never streamed before. In this way, it actually provides an advantage over using Twitch elsewhere. You can follow your favorite games and streamers as well, which will pin them to your home screen for easy watching.
If you're the type to get app achievements, there is some good news and bad news here. The good news is that the app is nice to use and the achievements aren't too difficult to get. The bad news is that some of them can be pretty time consuming and you will likely be going out of your way to get them. There are 10 achievements. 9 of those achievements are about time spent watching streams. The other is for watching a stream with at least 100k concurrent viewers. This list isn't exactly a crowd-pleaser. If you want an easy completion, you got it, but you still have to rack up 8 consecutive hours of watching one streaming channel and 100 hours of watching total, meaning you will probably be leaving your console on overnight. If you were hoping for achievements that are fun to earn, or any achievements at all related to streaming, following, or Twitch chat... You'll be sorely disappointed. It feels like a shame that the achievement list is rather boring when most of the features of the app are quite polished.
Overall, my biggest problem with the app is the bland achievement list. Other than that, it works very well and offers lots of good features. Hard to be disappointed with a free app that offers so much and rarely breaks.
Overall score: 4.5/5