The DX4000 is rather nice. It is a well made NAS that runs Windows Storage Server 2008R2 Essentials - a close cousin of Windows Home Server but capable of servicing 25 computers rather than 10. Most NAS systems run a variant of Linux; the choice of Windows means the box has to be more powerful plus the software is more expensive, but it is very polished and capable. The DX4000 has a lot of well thought out quality features; for instance, it uses enterprise-grade hard drives and has twin Gigabit Ethernet connections. It also has two connections for power bricks; unfortunately only one is supplied, but it means you can at least prepare yourself for a failure.
The question is: who will buy? The DX4000 is relatively expensive, at £799 for a 4GB model or £1199 for an 8GB one. This is not to say that it is not value for money - Windows-based NAS boxes are pricey, although it is also possible to buy it for less than this online. But the question is really: who will walk in off the street and pay £799 for one? It is not, after all, an impulse purchase.
Being able to buy such a sophisticated piece of technology in a retail outlet is an interesting development. It will be interesting to see how it pans out.