OpenSolaris as a file server
A very fast SMB/CIFS server and the modern functionality of the ZFS file system make OpenSolaris a good choice when setting up a LAN file server.
Building a high performance file server for your home network isn't rocket science: A reasonably fast processor, one or two GBytes of RAM, a gigabit network, an SMB/CIFS server for Windows, Linux and MacOS clients and a few hard disks in a RAID-5 array. This is achievable with £400 to £500 and promises more data safety and especially a much higher performance than a simple network hard disk.
To keep the cost down it is advisable to use one of the free operating systems that are capable of SMB server operation. Linux and FreeBSD even offer special varieties for NAS operation. But why not use OpenSolaris? After all, Solaris is a tried and tested server operating system that comes with ZFS; a modern storage solution combining RAID functionality and a Logical Volume Manager with a modern file system.