Apple just made your TV watching much easier... if you subscribe to the right services, that is. After dropping some hints in November, Apple has activated its promised single sign-on feature for Apple TV and iOS users in the US, but only for a handful of offerings. DirecTV, Dish and cord-cutter service Sling TV are the highlights among providers. Only some channel-specific apps can use SSO as well: A&E, Bravo, NBC, Syfy and USA are among the choices, and the option isn't always available on both Apple TV and iOS gear.
How well the feature works will rely heavily on app creators. There are some glaring omissions in the selection right now (HBO, anyone?). The situation might improve sooner than you think, however. Single sign-on might see greater adoption now that you don't need a beta operating system to try it, and there will be a stronger incentive to use it once Apple's unifying TV app is available. If support is rough around the edges right now, it might be a very different story in the months ahead.