Inside is 640GB of storage, expandable with its four rear USB ports. Like the rumors said, there are no internal hard drive slots, but there is Gigabit Ethernet. The internals are also less powerful compared to HP's higher-end EX487 machines, but is enough to run everything the bigger ones could before the recent update.
The question is, is $390 low enough to get people to jump on the Windows Home Server train? We think it is. It's not quite as cheap as to be throwaway money—you can buy a decent netbook for $390—but it is low enough to be worth it just for its OS X Time Machine capabilities alone, not to mention all its standard Windows-integrated functionality.
You can order now at eCost. If you wanted to give your relatives who don't regularly backup their machines an easy (networked) way to do so, this is it.