True, Intel's RAID-drivers are very fast with the 'enable write cache' (actually a write buffer) option enabled. It does come at severe risk of filesystem corruption should your system crash or have power problems while inside windows. So make sure you backup everything you cannot miss, but that should be done always and not because you're running RAID0 now. But with the added Write Buffer, which will use your RAM memory the same way as a hardware controller with its own memory would; the first X MB are 'free' meaning they go straight to your memory and thus are very fast. This could lead to a more pleasurable experience.
But, as windows tells you the job is finished, the Intel drivers are actually still hard at work at actually writing the data to the physical harddrives. Should power fail, NTFS's journaling will not protect you against the large write buffer in the Intel drivers.
Also, Intel's MatrixRAID would make it more difficult to recover your data should the RAID itself fail (driver issues, metadata corruption, design failures). With normal onboard RAID you can always use Linux or BSD cd and recover the data by software RAID abilities of those operating systems.
Be sure to avoid JMicron, Promise FastTrak, Silicon Image and such; their RAID drivers are a joke.
nVidia is a good second onboard RAID controller. GeForce 8200/8300 (AMD) and 9300/9400 (Intel) are something i actually recommend.