Probably not a bug but vehicles, even with fully-inflated tires, feel almost like they're dragging a brontosaurus behind them again. If I don't want to do a weird morse-code with the accelerator key to maintain speed I have to hold it down until I hit 90, release it and, when I hit 60 about 1 second later, start holding it again. A 30mph drop in 1 second without using brakes feels a little off (to me).
Also brakes don't seem to slow the vehicle any more quickly than simply releasing the accelerator.
Edit: I should have reported this earlier but I didn't want to sound like I was bitching.
Edit2: Watching Cromulent Archer and he's noting that, at least on the police car, the RPMs go up really high before shifting gears. Video at appropriate time: