Raid in a server is mainly used for data redundancy (ex : in case of a disk fail the server still up, hot-swap the disk with a new one and there you go). At home, like lagger said, you usualy want more speed but not expect as much up-time as in a server, so you go Raid 0, wich allow you to span your data on multiple disk increasing the write/read speed.
It's better to be rich and healthy than poor and sick!