It’s a great idea to free up your data, turn off a machine and also reduce power consumption.
I have one set up as a server – media and web – and it’s up to steaming hi-def and playing music all round the house.
The more you spend, the more capable it gets and more features you have but even the basic ones have all sorts of built in servers, for doing stuff like iTunes and bitorrent etc.
DNLA will also let devices connect and share content – my Samsung TV can stream direct from the NAS.
I upgraded from an IcyBox 4220 to a Qnap TS239 Pro, mainly for faster file transfer (hi res photos, large video files) due to the much faster CPU. Expensive, but if you are moving large files and backing up lots, it could be worth it.
However, the slower Icybox could still steam a DVD rip to at least two different machines at the same time and handled all my iTunes. Backups off the NAS to the network were a bit slow.
Don’t know if it’s of interest but the IcyBox is for sale, £45 posted, just needs drives.
http://www.bit-tech.net/hardware/storage/2009/02/01/icy-box-ib-nas4220-b-network-storage/4