Raid really isn't used to increase performance. It can increase it a little bit with RAID 0 and 5, but RAID is used more for data redundancy and protection.
I would prefer RAID 5 with a controller - so the processing isn't done by your processor, but the RAID controller.
It depends on your data, if you are in an office environment with a server RAID is a must IMO, if you are at home and can live w/ losing your Family Guy episodes and your songs then RAID probably isn't worth the cost and setup. Normally just a weekly backup to a few different disks and dvd's is all I use to backup my essential data like work files, quicken accounts, etc.