A new review on Tom's Hardware gives the once-over to the new chips from Intel that have an 200MHz (quad-pumped to 800MHz) bus.

The article's conclusion is that you see some substantial gains for data-heavy apps, but many others see only marginal gains from the new FSB.

I found the graphical depiction of the performance to be particularly interesting, as I expected the 800MHz FSB to blow away the 533MHz version at the same clock speed. In fact, it appears that in many tests, the two are basically neck-and-neck. There are obvious exceptions, but for the price- performance determination, take a good look at what you need and what you will get.