I've flown OTH-PDX, and it's a pleasant flight. The view of the Cascade Mountains when clear are outstanding. Your carryon has to be in the back of the cabin, or on your lap. I would look at the route map and select the window with the best view. I've heard you can get cell phone reception on a Seaport flight (wouldn't know about that ). It's like Southwest for seating, first come, first served.

One minus; they are not PreCheck capable yet, shoes have to come off.