I have a 2005, unrestricted with D&D (not cat) pipes, triple filters, and no secondarys. I get about 30 to 32 mpg, a little less if I'm really hammering her.
A coworker just bought a 2013 roadster and is claiming ~40mpg.
CanberraR3 has the realistic approach...as he said when the light comes on start looking for a gas station or at a quarter of a tank if you are in a more remote area where gas stations may be few and far between.
Fuel consumption on a stock R3 depends on cruise speed (RPM). If you cruise at 50-60 mph, then 38-43 mpg is easily possible. If you cruise at 75-80 mph, then expect 10 mpg less.
Also, I will say this once again - INJECTOR FLOW VARIES CONSIDERABLY AT LOWER DUTY_CYCLES. Don't expect all R3s to act the same.
It cracks me up when there's a question on fuel economy for a 2300cclong bike. Whem my Rocket was stock, I got close to 40MPG as well. With Jardines and a tuned PCIII, I get about 33 MPG.