What Raid do you intend to use?
Raid - 0 Striped for performance :
I have Raid - 0 and windows installs and loads slightly faster than standard HD setup. Game level loading also is noticibly quicker. Reliability is said to be questionable but I have never had a drive fail on me. If one HD fails then all your data is gone. Most commonly used raid setup.
Raid - 1 Backup : Never used this myself as this will half the disks total storage space as the data is written to one drive and then duplicated to another. The benifit is that if one drive fails you still have all your data intact backed up on the other drive. If Data backup is important to you then I suggest you use this.
Raid 0+1 : You will need more than 2 drives for this and it is basicly a combination of the above.
Unless you have a dedicated raid controller (most don't) you will be using an onboard controller such as NVRaid or Silicon Raid (both software), NV raid is said to be better both in terms of reliability and speed, a dedicated hardware raid controller will give much improved results but they are very expensive. There are other versions of Raid (5 and other combinations) but the above versions are the most commonly used.
Hope this helps.
