Indeed, if you look at widespread BH-5/BH-6 results across nForce2/nForce3/nForce4, most people's sticks go another ~8-15 Mhz higher in an nForce3/nForce4 board (it's more the Athlon64's on-die memory controller than the nForce3/nForce4 chipset mind you), versus where they maxed out on an nForce2 platform.
Reefa, my strong belief is that the Athlon64's on-die memory controller is what makes BH-5 fly for us. nForce2 and intel results are somewhat similar (seemingly depending on the memory PCB), and both use(d) a 'Northbridge' memory controller. Putting the memory controller on-die is one of the best things that AMD has ever done, in my opinion
With the DFI nForce4 board available to us, BH-5 is even more attractive, because we can easily give the ~3.6-3.8V needed to max it out. I'm making this statement based on the average price of BH-5 capable of ~250 MHz 2-2-2 - typically about ~$120 USD per half gig, give or take depending on the brand, and the stock speed (PC3200/PC3500).