I'm going to make myself really unpopular here and say that if you're not using the apple tv for airplay then there are probably plenty of cheaper, more functional alternatives.
(bear in mind in the UK they cost around $165, not $99, therefore the case is better for the apple tv in US)
But the "killer app"so far is linking to all your iTunes purchases. Roku is only interesting if you got a lot of your stuff from somewhere else... I won't call Roku pirates, but most of their customers were at the start. AppleTV had LEGAL CONTENT 5 years ago. Roku is entirely Dependant on Amazon or subscription services... They won't even pay for a YouTube License from Google which is the only other thing I use my AppleTV for.
They cheaper out on paying for ANY content, and that's what keeps people USING your device.. And Apple's 30% cut of media sales makes AppleTV VERY profitable just as an accessory.