I'm not sure of the features of your NAS but with my HP MediaSmart WHS It brings:
-Network Storage
-Easy Redundance with folder duplication
-Practically unlimited storage potential between the Hot Swappable SATA drives, USB ports and eSATA port
-An incredible PC Back up system that great for backing up multiple PCs. It wakes my computers nightly, backs them up, then they go to sleep again
-A secure HTTPS portal into your server for remote access to files, media and desktops
-A huge amount of plug-ins from a very active community
-Media Streaming through the web or to network devices and computers
-Basic Network health monitoring. It monitors what machines have up to date viruses (if you have the plug in), what PC's aren't up to date on patches, how long since their last back up, if local firewalls are disabled.
-I use it to share data with friends over the net. I have several accounts for them.
-Since it's basically win2k3 server, all the flexability that brings.
I'm sure the NAS you mentioned is a fine product. WHS is quite excellent too. I'm extremely pleased with it. I've been running one since last November and it has definately been solid, usefull and about as "set it, and forget it" as something like this could be.
I'm eagerly anticipating the next version. If they include some windows 7 features like "Home Group," and include basic Media Center features like Tuner support and allow Extenders to connect to them It will be my dream product. It would become my network centerpiece and be a central hub for all my media and data. Right now that work is split between WHS and a dedicated MediaCenter PC with a few TV tuners installed.