Wait a minute ... I thought from the article that this was "wireless" and "self-powered." It's not at all.
Sure it has a battery inside, but it has a SATA connection on the back and a power plug on the side. This will be plugged in almost all the time when it's used at home.
If that's the case, one might save a heck of a lot of money (as well as effort, time, complexity and futzing around), to just buy a USB device to plug into the Airport Extreme. Same thing, less money/complexity etc.
I revise my opinion from "cool" to "meh" on this one.
Except that won't do what this device does. There's really no comparison.
How are you going to use your Airport Extreme when you're away from home?