1. C2D is 64 bit by design. According to Intel, it features "Intel® Extended Memory 64 Technology." This is something Intel put into the chip to enable support for 64-bit applications and address more than 4gb of RAM - since no notebook can even have more than 4gb of RAM, this feature is pretty useless. In fact EM64T was available in the later Pentium 4 models. I have to be honest, I didn't realise that CD didn't have EM64T and I was unaware that this difference existed between the two chips. It might explain the 60 million transistor difference.
2. The specification of C2D (mobile) indicates that the FSB is 667 MHz. Apple didn't do anything about that. The desktop version of C2D does have a higher FSB (1066 MHz) as a matter of fact. You're correct, but the point is that for the C2D to make the most of its additional pipelines and Cache, it needs more bandwidth and really needs a faster FSB to be efficient. Such a motherboard will shortly be available for notebooks.
3. As for the clock speed, the mobile version of C2D ranges from 1.66 - 2.33, and that of CD is 1.06 - 2.33. You're right, but being a C2D doesn't automatically mean the mhz is higher.
The bottom line, and this is only my opinion, is that the C2D is severely crippled in a MacBook or MBP because
- The 64-bit memory addressing will never get used, as this only benefits systems with more than 4GB of RAM (in fact application that need to address more than 4GB of RAM, meaning a system with 8 or 16GB at least)
- The FSB severely bottlenecks the system, because the chip isn't getting the memory bandwidth it wants to run effectively
- No 64-bit operating system exists for Apple. Leopard supports 64-bit, but again this is largely wasted on 4GB notebooks with 677mhz FSB speeds.