Apple and its AppleTV is yet another product that makes it completely impossible for linux users to use without spending money getting a Windows OS or a Mac. If only iTunes were made available on Linux, Windows and Mac, then it wouldn't have made a difference but no…
Fortunately, a similar, or even better (?), device called Neuros OSD, is now available for roughly the same price as Apple's AppleTV. However, what makes it really better is the fact that it is completely open. Being the first open source Linux-based media center allows the open source developer community to extend the features of the device without voiding the warranty – very much unlike the AppleTV.
Take that, Apple! Until you support Linux with your products, I really doubt that you will get the Linux crowd's support as well. :)