It's a fine ride. Fun, kind of scenic, there will be some traffic but there are wide shoulders almost the whole way up and if memory serves the one place with narrow shoulders had two lanes going up. Drivers were very courteous, everyone changed lanes to give me more space.
But I wouldn't travel from another state just to do this ride. We have better. I'd do the North Cascades Highway or Mt Baker before Blewett and Sauk. But it's still a pleasant ride. If you're going to do it, you should also ride nearby Teanaway River Road to its end at 29 Pines (here it turns to dirt and extends about 10 more miles to the Esmeralda Basin trailhead) and if you have time, head north to Leavenworth and ride Icicle Road.