Yeah my bus tops out at about 75-77ish... I don't usually run it that fast becuase the fuel ecomomy drops significantly above 60. It also takes a long time to get up to top speed, so I usually try to go with the flow of traffic. If there's a vehicle in the slow lane I need to pass I plan it way ahead and get over soon enough that I don't have to slow down then speed back up. I hate it when a friend drives and tries passing cars like he's driving a regular car... I would imagine that uses a lot more fuel - constant slowing and speeding back up.
I know what you mean about the turbo lag, for the first few seconds (from a dead stop) it has very little power then when the turbo winds up... look out. I usually pull away from the normal flow of traffic at a stoplight about 1/2 way though the intersection.
I'd much rather have the rear engine, seems it'd ride a lot better. It gets pretty bouncy in the back of my bus. You have to be real tired to sleep in it while going down the road, like ready to pass out tired.