I have been trying to find this answer before buying an ATV2.
If I am watching a movie from iTunes to the ATV2 and my wife wants to watch normal tv, can I switch airplay to continue playing the movie on my iPad?
I like the idea of leaving the movies on the pc and not have to synch and play them from the iPad.
What you are talking about can be achieved with a very cheap iPad app called Air Video. You don't even need an AppleTV. It streams almost any video format (does live transcoding) wirelessly to your iPad from your computer. I use it all the time. Probably one of my top 2 or 3 iPad apps.
The new version can even play iTunes protected content if your device is authorized for that account by playing it through the browser.
Best part is that it is a universal app which works on iPad or iPhone...
http://itunes.apple.com/us/app/air-video-watch-your-videos/id306550020?mt=8