How do you backup the data on the one external drive?
Edit: I see that it has two USB ports, so I would assume multiple hard drives can be attached. Hopefully some kind of backup can easily be launched that would mirror one drive to the other.
Personally, I try to avoid devices that combine functions wherever possible. To the point that I have the following on my home network, in addition to PCs, laptops and network music players:
1) cable modem
2) firewall
3) network switch
4) wireless access point (not a router)
5) file server
The first four are all small boxes, plus wall warts, so even if you're space limited, there's not much difference between having four and one. The file server sits in the basement.
Last night we had a big snow storm and I lost power momentarily. When power came back up, the wireless access point must have gotten zapped (it, or its power supply). So I'm just missing wireless right now, but still have internet access, and access to the files on my network.