Related to AppleTV: I've been using Beamer.app (http://beamer-app.com/) to stream unsupported content to AppleTV. It's a premium product, but it was worth the $15 (or thereabouts).
The freedom to leave the house and to preserve your battery life is another issue. I often fling videos to my chrome cast for my kids remotely. AirPlay style mirroring is wasteful of bandwidth, battery, it double compresses streams, and adds latency.