I could be mistaken, but when they say you can access "your music", I think they mean access to your Apple Music account, and when they say "your photos and videos", I think they mean access to your content on iCloud. So, if you are looking to access material on your NAS or your other computers, I think it's a no-go. Unless I am misunderstanding, which is quite possibleJust checked the Apple site and there is a whole section about being able to stream your own content. It doesn't say how (Home Sharing vs. Airplay) but I am offically less concerned than I was earlier about being able to watch my own content as I have been able to on all previous AppleTV's.
http://www.apple.com/tv/music-and-photos/
Phew!