The KT4 Ultra is a really nice board loaded with features - but it doesn't represent any sort of performance leap or overclocking flexibility over KT333 boards that are still being released. The most anticipated features didn't yield performance increases that we were hoping to see. DDR400 was mostly a disappointment - though we may see better results once CAS2 PC3200 RAM becomes commonly available. AGP8X also doesn't create any kind of excitement. Maybe when Microsoft officially releases DirectX9.0 with AGP8X support you will see something different, but for now current day applications will likely see little improvement.
Review Link : Neoseeker