So, we know already that we can install AppleTV`s BackRow on Tiger and use it as a FrontRow. Just download an installer, double click on it and you can enjoy your AppleTV on your Mac, instructions can be found in my AppleTV on your Mac/Hack post.
AppleTV is not a mature product, and Apple people know that, by calling it a hobby. At the moment aTV was released it could play only QuickTime movies in SD. So basically people where tied up to iTunes and old Standard Definition format. While ago Apple updated aTV and to be able to play HD content (720p only) and surround sound. But people where still tied to iTunes contend or they had to convert movies to QuickTime format. There are definitely better players out there, which can play 1080p HD content, have better sound quality and so on, bu there is something special about AppleTV - it`s operating system. Yes, aTV is actually running modified version of Tiger. As you can play Dvix on your normal mac it was easy to get this function to AppleTV, the best plase to look for some instructions and guides is hackint0sh.org. If you don want to do it yourself the Guys from Apple Core LLC made aTV Flash and you can buy it for 60 bucks. They even guarantee that it will work with Apple updates.