RAID-0 mainly only benefits sequential access, so the first question to ask is whether or not you access a lot of small files or fewer large files; it's the former for most people. Aside from that, the drives are already pretty fast, so even if you do see an improvement, it isn't likely to be noticeable except on the largest files.
The trade off is that you are more susceptible to failure, since there's more things to fail, and any single failure results in ALL data being junk. Also, boot times have the potential to actually increase if you are using a hardware or firmware (RAID setting in the BIOS) since the array has to be initialized first (a software RAID setup under the OS won't suffer as much, but also isn't accessible outside the OS environment). The overhead also tends to increase latency as well which worsens random access times.
So, basically, unless you are moving big files back and forth all the time, a RAID-0 setup could actually prove to be detrimental.
If you are interested in doing an array, you might instead look at a RAID-1 setup. While I'd never suggest it replace regular backups, it does provide data redundancy, and if your hard/software is capable of simultaneous disk access might improve access times under load by allowing each drive to serve different requests (a second drive to handle requests is only useful if requests are coming in faster than a single drive can service them), though, as above, you still have a penalty from the array overhead.
