I've ridden the Oregon coast several times. The scenery is nice and all but I don't find the riding particularly thrilling. Also I usually ride to CA and back in the fall/winter/spring. Having everything between SF and Seattle be non-raining then is not so common so I focus my planning around NorCal being dry so that I can have fun on 101 and 1. I just slog it through the crud to/from Grants Pass or Yreka.
I-5 doesn't bother me. I just get the Ipod going, set the cruise control and kick back. I've also driven it numerous times so it goes by quickly and before I know it I'm in Grants Pass.
When I rode down in October taking I-5 to Grants Pass let me make it to camping on the coast at the northernmost spot on Hwy 1 in one day. The next morning I awoke to the surf and the knowledge that I'd be riding Hwy 1 the entire day. I live for days like that.
When I ride home in early April I'll consider the OR coast since I haven't ridden it in a while but if it's raining then I'll just slab it to get home.