It's funny how many comments have zipped right by the first page of this thread where a post seems to lay waste to the theory that RAID 0 offers no improvement in performance. It seems like for enthusiast computer users, the average gain is about 46% vs. non-RAID performance.
Booting Windows is a big gain. Defragging is a big gain. Loading game levels is a huge win, especially since the average game going forward will be more than 3 to 5 GB, with single texture packages a few dozen to a few hundred megabytes each.
In addition to the stripping, which by simple logic dictates faster performance on average, you are also talking about 16 MB of cache vs. 8 MB. Depending on the app, that is also a big win.
(has some interesting results).