[martinced]

"Is there something about newer CPUs such as i7 that makes virtualisation hugely faster and more responsive?"

Well you probably could set the CPU affinity of every single application that is not the VM to one core and set the CPU affinity of the VM to the three other cores. A tiny script doing that should be fairly easy.

Maybe someone who knows VM better than me could tell if it would work or not?

Now my experience with VMs do not match yours: I've been running Windows just fine inside VM providing it has enough RAM (but RAM is basically given these days) and provided the special drivers were installed to make the UI fast.

Also, I've read professional photographer use Octocore Macs with 20 GB of RAM and create gigantic ramdisk for Photoshop and saying that it is incredibly much faster than letting the OS be "smart" about what/when to page to disk.