Sweet
Here's my setup!
2.6ghz G network on the superhub.
This connects to an Airport Extreme running in 5ghz N wireless.
My 2 imacs are connected to the airports 'N' network. All the other devices such as xbox, wii, ipad, phones etc all connect to the 'G' network.
I know i could have 2 wirless networks on the superhub, but I have 2 1TB hard drives and a USB printer connected to the airport extreme so still need to keep that in the loop.
Anyway, its all working spot on and am getting the full speeds as shown above through the wireless on the airport extreme!