The DROBO (Data Robot) is way more than a bank of hard discs as many other NAS boxes are. This is a self managing system that looks after itself for you! I've been eyeing these up for a while now and tonight came home to a dead external disc (Lacie :-( ) so went in search of somthing better.
Prices are reduced on the USB only ver as the firewire+USB is now out though for anyone with a home network, there is a DROBO share unit that will hook you up to a gigabit network still!
To understand what it is really about take a couple minutes to watch this video :-) http://www.drobo.com/Products/drobodemo.html
P.S. before someone replies saying it doesn't come with any hard discs!!! YES, you would be correct. The idea is you can add what you want, when you want... I bought 3x500gb Barracudas (7200.11) with it on their today only £39.94 a peice.