I bought Discover 125 Disc 1 month back, my primary concern was mileage.
I checked my mileage using reserve to reserve method( filled 500rs of fuel=6.33liters) I got 479.8KM, i.e 75KMPL(in city), very happy:) with the mileage even before first service.tried to stay on 5th gear and below speed of 45 kmph. it gives very comfort ride as I have to travel 45 km up and down daily.
Only disadvantage is that Gear system is not that friendly, say if you are in 5th gear and you sudden of slow your vehicle and try to come to 2nd gear, it stuck up in 4th gear, I have to go back to 5th and come down.(this happens not always but say at random). hopping that this issue will be fixed after first service(as told by one of my friend).
Overall, a great bike .
They have released discover 125 ST with lower price tag, I should have waited for this bike.