State highways has done a lot of mods to SR-20 over the last 5 years and it isn't a big deal these days. We much preferred it over the narrow, winding US-2 with all the big rigs and the steep drops to the river going east-bound. DW wasn't comfortable being on the edge of the drop-offs.
Sure, the top of Washington pass is 1000' or more higher than Stevens, and it might be an issue if your rig has a carburetor engine. Maybe the fact that we live out at the west end of the SR-20 spur in Anacortes colors our judgement a bit!