everyone's talking about DDR400 memory controller... blah, blah, blah.... the truth of the matter is that there's nothing wrong with NVIDIA's memory controller, and there may or may not be a problem with VIA's. i don't know as i haven't tested a board.
the problem is with DDR400 memory; it's latency is significantly higher than that of DDR333. no one makes a cas2 (or even 2.5) DDR400 module, so you're talking at least 3. add to that other memory timings are far less agressive than DDR333's and you're talking about spinning your wheels, if not putting it in reverse.
DDR333 is still the sweet spot. DDR400 will do you no good for either chipset.