@katesegrin definitely the ability to display chat alogside the video stream. Haven't seen other websites/extensions that would provide the same functionality. Up until finding TwitchCast I've been using Twitch's Android app to cast streams to my TV (leaving the chat open in the app). Many streamers interact with the chat directly, so not being able to see it left me feeling I'm missing out on something. Not anymore! :-) Besides that, being able to manually change the stream's quality is also a great addition as the official app or website don't give that option while streaming through Chromecast. You're being left with 'auto'.