I bought one of these several months ago, and I have to say that in that time I've been fairly unimpressed with the device.
Firstly, it's certainly not "ultra-silent" as the blurb suggests - not even close. You wouldn't want it in the same room as as your TV, for instance.
Secondly, the data transfer rate is abysmal. Even when connected back-to-back with a gigabit equipped PC, It can barely manage 7megabit/second transfer (I suspect the transfer rate is actually limited by the speed of the drives, rather than the network adapter). But it you want to store DVD-quality video, this is far too slow.
In short, steer clear of this and spend your money elsewhere