These are good for home or SOHO networks
I'd highly recommend the Infrant NV+ (now Netgear) for SOHO use as its simple and reliable and if you add a proper media server software (TwonkyVision comes to mind) you can stream anything to an XBox 360 / PS3.
For 'serious' use I find a Buffalo Terrastation Pro II is better as its lower cost, runs on Linux and so easily 'improved'. even then I'd only use them for primary back-up.