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.