I grew up in Jackson and traveled US 12 quite a bit, there are some neat historic places along the route, but don't be rushed for time! You will end up behind a slow tractor trailer or maybe even a tractor. Stop at Freddies Freeze in Somerset
Freddies Freeze - Somerset Michigan - Food, Sandwiches, Ice Cream
As someone noted before check out the Irish hills stagecoach stop, MIS, then Freddies Freeze for lunch. West of there it gets a lot more agricultural as opposed to wooded. Too bad you aren't going through in the fall Flavor Fruit Farms grow excellent apples.