Roku ($29.99 - $99.99): One of the pioneers in the concept of cheaply and simply turning any TV into a streaming portal, Roku offers a wide range of products, from simple sticks to bigger (yet still compact) boxes. Because it’s been around so long, Roku has agreements with pretty much every major and minor streaming video service, and it is even integrated into some smart TV models. The company has also been giving its customers more power to control the sound of what they’re watching, with features like “night mode” (which mutes explosions and amplifies whispers) and “private listening” (which allows viewers to watch a show or movie on their TVs but listen to it through headphones).
The question of "when does it make sense?" can easily be rephrased as "how much money can I save?" and one of the biggest factors will be the price difference between combined internet and TV service or just internet. These are also the options that vary the most widely based on where you live, and the availability of promotions or contracts that can keep prices down for a short time.