I think the real benefits occur when you can actually use enough heat to practically vaporize the fuel, without causing the side effects. It will burn much cleaner than liquid fuel.
Remember these guys?
FuelVapor Technologies - fuel efficient vehicle automobile high mileage ale'
For those wanting to experiment, I'd say you would want to safely route exhaust heat to the fuel rail, and then maybe insulate it too. I dont think coolant temps will be enough. The best results would come from being able to re-tune the A/F mixtue maps with a laptop (a-la-moates). I imagine there will be some side effects to deal with, like spark plug wear, O2 sensor wear, higher NOX emissions.
Someone is going to do it though. And its going to be great.