I was thinking the same thing. looking for a new NAS since LaCie has decided to drop support for my d2 NASand it doesn't work with mac os 10.7's AFP
in any case I have a first gen appleTV kicking around just using it for internet radio on the stereo in my workshop right now, have the second gen hooked up to the TV.
I think the ATV would be ideal for this usage, for it's size and low power use and it just looks nice (and matches the two external drives I own too!)
it has a 10/100 ethernet and wifi(my network is only 10/100) and USB 2.0 port processor is a 1GHz PentiumM so in theory it should work, right?