The problem then is that you have you have to have your computer turned on and have iTunes running. Not a huge inconvenience, in the grand scheme of things, but if I'm downstairs and decide I want to watch something, I then have to run upstairs and turn everything on, log on, start up iTunes and then go back down again.
With my current AppleTV I have the internal drive full of my favourite movies and TV shows and it works quite happily as a stand-alone device. If I buy movies from the AppleTV they eventually
get synced to the machine upstairs and backed up, but I don't need to worry about the other machine being switched off or going into standby .As for the "instant streaming" from the web, that's great if you have a decent connection. If not, with the old ATV you could start it downloading and then watch the whole thing later when it had finished.