If your home is festooned end-to-end with Apple iPhone, iPad and MacBook Pro users, then the Apple TV makes sense. Why switch horses now?
However, for everyone else — and even Apple fans who want more out of their TVs — the Roku 3 is the clear choice. It offers more entertainment sources than any other streaming-media player on the market, and it's fairly priced and easy to install.
As it stands now, Chromecast is attractively cheap and has the potential to grow. However, the device is aimed at a completely different kind of TV viewer — one whose principal screen is on their phone or tablet rather than their TV.