Thanks, chaps, that helps a lot.
I'd come across a few memory benchmarks and although very few tests revealed any real difference I still wasn't sure whether the Core i7 860 itself would be crippled or not.
What I'm learning is that the integrated memory controller on the LGA1156 architecture disconnects the CPU speed from the memory clock speed (I think, is that right?). So the Core i7 860 would still perform at its best under 1066Mhz RAM, even in Turbo Boost modes (again, am I right?).
As for my usage, I do a fair amount of 3d rendering and this is all CPU-bound. Oh, and quite a lot of gaming
which again doesn't seem to be affected a great deal.