Raid0 helps ALOT. It can get very fast. Raid0 is ideal for 10000rpm SATA HDD. Raid0 splits data in half, then sends half of everything to each HDD. So it loads 2 times as fast. If you have a serial sata 10000rpm HDD, then your loading times would decrease eminently! This is how i usually explain Raid.
Pretend you have to run a mile. Now pretend i CLONE 2 of you, and each one of you run ONLY half a mile. That means it only takes you to run a MILE, in the time it takes you to run a half mile. Thats how raid works.
Now Raid0 can always get faster. If you wanted extreme HDD speeds, then you can get 4 serial sata 10000rpm HDD. That means the work would be divided equally between all four drives. Witch the task from your HDD would get done at 4 times the original rate!