Hi
RAID 0 is actually worse than any other solution. Example: Two drives spanded across two drives doubles the risk of you having a complete disk subsystem failure. With two drives you are twice as lickely to get one fail and becasue you have spanned the drives using RAID0 then you loose the lot. That's correct - If one drive fails you loose the lot (whole raid).
Your friend was correct - it is fast, but at what cost. Disk drives are cheap as chips, so a raid 1 or alternately just split you OS, SWAP file and Data onto different drives - you can have good performance this way if redundancy is not important.
RAID 0 is rarely used these days, due to people having issues that I mentioned above. RAID1 (Disk Mirror)or RAID5 which is a higly redundant striped raid set and far more common. These have pro and cons so a number of businesses are starting to use RAID10 (sometime known as RAID1+0) which is a combination of Raid1 which is stripped like RAID0 - this solution is both fast and redundant but way beyond the home users budget.
Good luck
Dave