Step 1: Support Core i7. Step 2: Support Triple Channel DDR3. Step 3: ??? Step 4: Profit
With Intel launching a chip touted to be the most advanced available, Asus, being the fantastic manufacturers they are, had to step up to the plate and build a motherboard not only worthy of the chip, but maybe even a little bit too good. Being touted as a "flagship" model motherboard (essentially, the penultimate of the companies offerings), the board supports all of the latest and greatest new and emerging popular technologies.
Let's turn our attention to the six DDR3 memory slots. Not very many motherboards are available yet (as of writing, 2/25/09) that accept the newest standard in DDR3 memory. The question on everyone's minds though, is if there is a significant speed advantage being offered in DDR3 at this time. The fact of the matter is that, unless you opt for a significantly higher speed than your current DDR2 implementation, the performance boost is going to be negligible, if not non-existent. Newer DDR standards always bring with them a significantly higher latency, and DDR3 is no exception. This cuts down any significant performance advantage in the entry level speeds (DDR3 1333) over the top end of the previous standard (DDR2 1066). While this Asus board claims to be able to support DDR3 speeds up to 1800 MHz (which would offer a significant performance boost) this requires you to manually overclock the memory bus in the BIOS settings of this board, and the 1800 MHz overclock is said to be unreliable at best. Additionally, there is already DDR3 speeds available at 2000MHz and higher, so we're not even getting "the best".
There is one significant advantage we're looking at on this board, and that is the triple channel memory support. You'll notice that the Rampage II has six slots for RAM, and each pairing of slots has a dedicated channel. Of course, you lose this benefit if you don't install three or six modules, so keep that in mind while shopping. It is always faster to install RAM in dual-channel, and now that we have triple channel the same rules apply to it.