For a couple of years we have been using a Dlink NAS at the office – without too much trouble, its interface is a bit clunky, and there were some problems with my Windows 7 laptop when I first got it, but other than that it has worked fine.
As part of our new Distaster Recovery service to clients we have been specifying Iomega NAS boxes, as the storage on the Dlink is starting to be a limiting factor I replaced it with a Iomega StorCenter ix2-200. The 4TB model set up for mirror raid, giving 2TB of storage.
It is an excellent box. Easy to use and configure, I have allocated space to the company with various levels of access as well have having space for the family to store images and media. I have it protected by a UPS controlled from the NAS.
One of the things I am lookking forward to is the availability of an iPhone client so I can make full use of the cloud services installed on the device.