The procedure below works if you want to carbon copy the whole system HD.
I transferred all my data, application and system from my old iMac 20" 2.66GHz core2duo to the new i7 iMac. I connected the new imac to the old one using firewire cable, turn the new iMac on while pressing 'T' (Target disk mode), and use the disk utility application in the new imac, and restore disk (the old imac HD as the source, and the new iMac HD as destination), A couple hours later, voila, I have all the presets, preferences, accounts, applications as my old iMac.
In my case, it probably works because it uses the same intel based processor and no major hardware differences. Try your luck, but as always, please back up first before do something major like this. Hope this could help. ;D