Mine varies, if I ride long trips on motorways I get close to 200miles out of the tank. I won't push it beyond that point though! Normal use around the island here with lots of gear changes I get about 150miles with the fuel light being on for about 10 miles or so. So I guess 35-55mpg.
On my 2000 ST2, I get about 40 mpg. Sometimes it seems that the gauge drops quickly, other times, it seems to drop slower. But based on mileage-since-fillup/actual-fuel-to-top-off, I ususally get 40-43. I've ridden at least 20 miles with the light on and the LCD gauge showing nothing. I'm not sure how much was left, since I filled up from my own ethanol-free tank (so I don't know how much I put in).
I love the ST2. If I had to have one bike, that would be the one.