Consider:
1) SR uses an 800 MHz FSB instead of 667MHz, but no manufacturer currently offering an SR-based laptop is using DDR2 800 MHz RAM. Does it even exist yet? Since only 667MHz DDR2 RAM is currently available, what IMMEDIATE reason is there to upgrade to a chipset offering an 800MHz FSB? Only those of us looking far forward to upgrading memory would want the option of an 800MHz FSB. For all others, there is no benefit.
Memory companies have zero reason to advertice memory before there is a machine that can use it. Samples been out a while and the specifications for the memory have been know a while.
The memory will be for sale soon after the systems that accepts them are for sale.
The memory bandwidth is significant and the extra address space (4 Gig) welcome by some of us looking for a superb MBP.