We took the Light rail to the airport this past Friday and it worked really well. In case you are curious on the actual times instead of just what is posted on various online schedules, here was our experience:
10:30: a neighbor gave us a ride from our house.
10:35: arrive at the Columbia City station
10:41: on the Link Light Rail
10:56: at the Tukwila station
11:00: on the shuttle
11:11: at the airport
$2 each person
a Thank You beer for our neighbor who drove us
and ZERO parking costs!