If you take a late nightflight (~11/11:30pm), be prepared for long security lines up to 40 minutes. They close down half of the entry points. Allow extra time if your airline's in a satellite gate.
*Being your own pillow and blanket for the flight. *Just because it's hot where you're goin, doesn't mean it's hot on the plane. If you board wearing next to nothin, prepare to freeze on the plane.
I was at BNA, DFW, LAX, SFO, and SEA in the same week. Only Seattle had a ridiculous security line. Don't come through without having pre-check or plan for a full hour in security.
one of the more painless ways to get away from Portland is to brave the connection through Seattle - well worth the extra range and sometime price savings
Sadly, the train at the airport is the most traveled Seattle mass transit. We've voted most every other effective method down in the polls. Enjoy that ride :)