RAID 0 is nice and it will increase your HD bandwidth and it is quite noticeable if you work with large photoshop files. For example I am scanning all my old photographs. It is easier for me to scan multiple pictures at once and then break them up in PS. These files are huge some approaching 2 gig. I do notice the speed difference between my main PC and my backup PC as the backup does not have a RAID array.
However, running RAID 0 is risky. You are doubling the odds off catastrophic failure affecting your data. If either disk goes, your screwed and restoring stuff from your backups. So, if you really want to go RAID 0, I recommend going either RAID 0+1 or RAID 1+0. It takes more drives but give you the speed boost with the addition of redundancy. That way if a drive fails, you simply replace the drive and there is no data lost.