Just for clarification to everone, the Xserve RAID is NOT a new server machine. It is simply an external drive array, for use on a network that requires the storage space of up to (14) 120 GB drives.
In a network/server environment, the benefit of the Xserve RAID is that every single computer on that network can store/share files on one device. That way, each individual machine doesn't need it's own massive storage. By sharing, the costs are optimized into one specific storage unit. You start off with a few drives, and add more as needed.
Long story short...the Xserve RAID by itself is equivalent to nothing more than a massive external hard drive. It is not a computer...not a server...does not replace the Xserve in any way. Without something to connect to, it's pretty much an expensive doorstop.