Starting next year the PDX-SEA QX shuttle will be moved to all Q400's. This will not happen quickly though as we are still waiting for the new Q400's to be delivered. Either way that route has A LOT of cancellations and really high load factors. Several of my friends do it and say it is one of the hardest commutes out there. One good thing is that if you check the flight loads and can't make it you can easily drive it. Driving is actually a great option because you can leave when you decide to.