Well, i'm going to have to disagree with those that say that RAID 0 doesn't increase performance. I believe it does. And i've read many articles that agree with me. It isn't a HUGE noticable increase, but it is an increase none the less. RAID 0 writes data evenly across 2 identical drive. NO REDUNDANCY. Yes, if one drive fails they are both useless.
But, by writing data evenly over two drives, it has been proven in many tests that the read performance increases by as much as 12.5%. In the end, you might save 2-6 seconds in load times. For a serious gamer, that's enough for him to choose RAID 0. Also, RAID 0 arrays with a SEAGATE NCQ are the way to go.
If you want safety, go with a RAID 0+1 / RAID 1 / or RAID 5 "RAID 5 requires 3 or more drives, normal 4. If you have 4 (200GIG) HDD's in RAID 5 you actually only have 600GIG of HDD storage. A small portion of data is spread across 3 drives and the 4th drive stores parity of all those other 3 drives. IF one drive fails, you remove it, and plug and play a new SATA. Very expensive option though. Mostly used in Servers.