Mileage - 38mpg avg on "all roads" (from 25mph to lose-your-license
), low/mid 40's on tours at reasonable speeds (<75mph avg). Expect the fuel light to come on around 160 miles and plan on walking after 200 miles. That's the price you pay for those 150 ponies.
Note the above mileage figures are with a stock bike. Full Termi w/ race ECU, Bazzaz, etc will richen things up and consume more fuel, so the numbers will go down.
Current: 2012 Moto Guzzi Stelvio NTX, 2008 Yamaha WR250R
Gone: Ducati Multistrada, Moto Guzzi Norge, BMW R1200GS, BMW F650 GS Dakar, KTM 520 EXC, Suzuki DRZ400E, and the list goes on.......