I stayed at the Westin Seattle last year on a free Friday and free Saturday. As a platinum, I didn't receive any sort of upgrade that I remember... maybe a higher floor? The room was only OK.. it was obvious that the room was quite old... but the view was decent. Was this once Westin's flagship hotel?
The other things that I recall: no Club Lounge, and they also tried to charge me the "energy surcharge" despite the fact that it was supposed to be covered by the free Friday and free Saturday.