My best range has been slightly over 57 miles. Very hard to do, though. You need a nice 40 mph main road with very little and well timed traffic lights.
I have been pulling off 47 mile round trips to the inlaws pretty consistently now. I find it amazing since I would normally take the highway and it would be a 60.7 mile trip. With the Volt I take this nice main street, it takes about 5-10 minutes longer, but cuts the distance down and I am able to span the distance without using a drop of gas. We leave at 2pm and come back at 11pm. A pretty good ride.
This last trip, I went 47 miles, used only 9.0 kwh, still had 8 miles left of EV range. Cost of only 0.70 cents in electricity. A trip that used to cost me $10-$12 in my previous vehicle driving the highway.
That is not the only benefit. The Volt is also smoother, quieter and has more useable power available. Useable is hard to explain. I guess you just need to drive a Volt to get it. No searching through gears or downshifting or sound of the engine stressing or loud exhaust. Just a quiet burst of energy instantly.