This device world be a pretty cool server if you could put your own OS on it -- kind of like a much faster Raspberry Pi with built in wif, flash storage and PSU
If you factor in the case + better specs, you'll find that it's a good value. I played with this idea a bit. I disabled unnecessary services, etc. Got it pretty bare ... but it's very hard to get a proper toolchain going. In the end, you'll need to cross-compile everything and doing everything right can be a real grief. It's really not worth it unless you can shoehorn Linux in there ...
This is not new. SheevaPlug, TonidoPlug and all the other variants... an ARM ~GHz CPU, 512MB of RAM, USB and ethernet in a 4" case. It runs Ubuntu and only draws 3 watts of power. I've had one running my nightly server backups for years. Cost less than $100.
Most of those don't have a decent graphics card that can run 1080p video and do H.264 decoding in hardware like the AppleTV. They make great Linux boxes, but are lacking in the media center department.
All of those plug computers have massive heat problems. Also, although they are frequently rated in the GHz range, their actual performance is absolutely terrible. The Apple A5, on the other hand, is a real workhorse with no heat issues.