We have a long-time relationship with Quality Inn SeaTac.
It's comfortable, quiet and clean. Breakfast is good, and the staff are friendly.
Depending on timing, waiting for the shuttle from the airport can be a bit too long. In chilly conditions, our wait was a bit over 30 minutes, and it was cold. Next time, when I call for the shuttle, if it looks like a wait, I'll go back up to the cross-bridge that looks down on the shuttle pickup point 1D, and then head down when I see it coming.