Plenty have already been written about the Apple TV, on how its features are limited and will be a massive flop to how it will revolutionise TV viewing. I think I agree to both point of views, because how you feel about Apple TV depend heavily on what TV is meant to you and how it fits into your life.
From the traditional TV viewing point of view, Apple TV is a strange beast. It is not a DVD player or a DVR, so it is not about replacing a piece of equipement that we already own. Apple TV 'merely' plays content from your computer on your TV, be it video purchased from iTunes Music Store or video ripped from DVD, etc. Nothing revoluionary there, is there?
But if you look at Apple TV from another angle. One where video content are no longer served by the few TV networks and I think this is where Apple TV will be the watershed device when we look back in 5 years time. DVRs, and to some extend DVD players, have changed TV viewing for many people. We are no longer tied to the TV schedules defined by someone working at a desk in the network. Now we can record shows that we want to watch and then watch them when we want to. If we take this one step further so now we also control what will be shown on the TV, this is what makes Apple TV so special and may take a while for content creators to recognise.
With video podcasts on iTunes, Joost, and other P2P 'sources', we are no longer tied to content any more. We are now empowered to find content that we want to watch when we want to. Of course many people have been doing this for a long time but it is not simply a few clicks of the mouse button and most consumers neither have the skills nor the time to find content this way. Apple TV, I feel, is the device that will bring consumer awareness to the possibility of decentralised TV content. And this raise in awareness will finally force content providers (TV networks, movie studios, MPAA, etc.) to realise the old model can no longer be the only model. The cat is out of the bag and if the content providers want to be rewarded for content they created, they need to help us find content that we want to watch, not actively blocking us and force us into the old revenue streams (TV, movie theatres, DVD).