I rather like this site's description of RAID. No nonsense, no frills, just the basic facts of what it is and then some suggested uses.

With a RAID-0 setup, you have an increased chance of losing data compared to if you just used 1 drive, because with RAID-0, if any drive in the array goes you lose everything.

Personally I think that Raptors cost far too much for only a little performance benefit, so if you want value for money, the Seagate Barracudas are pretty good performers and so is the Maxtor DiamondMax range.