Whether to set up a computer using RAID-0 really depends on what you want to use it for, and how important your data is.
As a general rule, RAID-0 increases the Read and Write speed x the number of Disks you use. As an example if you use 2 Disks in RAID-0, both read and writes will be twice as fast, 3 Disks, three times as fast.
So, if your SATA-II HHD drives average 75-100 MB/s, 2 disks in RAID-0 will run 150-200 MB/s.
Just for comparison, recent tests showed SATA-II SSD's (Read and Write speeds are different) averaged 250 MB/s, SATA III (OCZ) run 468 MB/s. These are very general averages but give you and understanding and comparative numbers to think about.
So, if you are playing computer games, you will notice a speed difference for sure, if you are doing Excel spreadsheets you won.t