I went the NAS route with the goal of getting all my iPhoto libraries (new one each year) off the computer (filling up) and not having an external HD connected to my nice and neat iMac. That seems to have been a failing proposition. Even though I can use the iPhoto library, doing it over wifi has been a chore. It's okay on the computer directly connected via ethernet to the network hub where the NAS is.
BUT, the main goal of buying the ATV2 was to be able to show all of those spiffy pics of our son to the grandparents when they came to visit. I have yet to get ATV2 to play the photos that are stored on the NAS - even though all the home sharing stuff is set up correctly, iTunes is running (seems a dumb way to see my iPhoto library), and all the other settings. It simply seems to be unable to play the photos from the NAS - even though the computer can.
And don't get me started about not being able to play any of the hundreds of avi movie container/files produced by our Canon PowerShot camera. Movies that play absolutely fine on the iMac with no special software (beyond quicktime).
My NAS is becoming more and more a place to just do backups and the mergining library functionality shared between multiple computes and iOS devices seems to be a lost cause. very frustrating.