I lived in Seattle for a couple years a lifetime ago. My brother has lived in Eugene for about 30 years. It is true that Oregon is rather progressive and Eugene has a lot of regulations that other towns, other states don't have. Eugene attracts "free spirits" who seem to loiter in the downtown area. If you are open minded, you will love it. Everyone has a dog, lol.
The humidity is very low, and the summers don't normally get very hot. And if they do, it's not like humid Midwest or southern heat. My brother doesn't even have AC, and we were fine there in late June.
There is no sales tax, but I think other taxes are high, and the unemployment rate has been high, although with the economy now, the job market may be better than it has been. Houses are pretty expensive, as a lot of people have moved to Oregon from California, making houses more scarce.
If my and my DH's family didn't live here, I would move to Oregon in a heartbeat. The forests are so beautiful, and the weather more to my liking, the general "vibe" is relaxed and the philosophy is more progressive than the Midwest. If you love being outside, go for it!