Tech Hounds posted an article on Vista's I/O Performance
Looking at Vista's I/O Performance
Originally, we set out to compare various RAID and AHCI SATA controllers and what kind of performance we can expect with Vista. But problems during testing lead us elsewhere - this article. These preliminary testing clearly shows that kind of comparison is just not possible right now - something is still definitely broken with Vista's I/O performance.
Looking at Vista's I/O Performance