This trip covers almost every climate in the beautiful state of Washington except coastal and rainforests.
This trip (especially in Spring and Fall) can go from temperate to freezing to rainy to bloody hot so bring the right gear.
Stevens Pass is beautiful in both directions and a little different in each direction. Lots of sweeping curves, rivers and a few waterfalls.
The East Cascades remain winding along the river with a few straight spots until you get to Wenatchee.
Along the Columbia river there's lots of rural scenes and several straight areas in the less farmed areas.
The straight shot from Coulee city to Waterville is known as a good place to open her up. But be aware, the staters know that, too.