As compared to a fast single SATA drive? Load times will improve, so you wait 5 seconds instead of 7 for a level to load. In game play, no help at all.
RAID was favored more a few years back when drives were quite a bit slower than they are today, and 512 meg was a lot of memory. When you look at the speed of a good SATA II drive, and throw 4 gig of memory into the mix so the game can load an entire level into memory, RAID kind of falls by the wayside as being much of an improvement.
my experience so far is that a raid 0 of 2 or more drives will load a game or maps in a game faster that a single drive of the same type (make and model) , and the only improvement while playing a game is if you do not have enough memory to load the whole map/game and then your machine has to access hard drive for more information while playing.
so if it is important for you to be the first to your favorite vehicle and you more than enough memory .... then a 2 or 3 disk raid 0 will be great for you.
just remember to back-up ANYTHING that you think is important.