It's very useful.|
Right now, I'm sitting downstairs at the kitchen table, wishing my Firewire array of drives were network attached so I could check which episodes of Raising Hope I'd already seen. Going upstairs with the computer is not an option, unfortunately.
Only downside is, network drives are painfully slow, at least relatively, to locally attached storage (except for USB2. If you only have USB2 you will not care one way or another).