We do fly through SEA a lot (not so much now PDX since they discontinued all EUG/PDX flights), but they are connections with not a whole lot of time. And the same Amex gives us "free" food on board the AS flights so I've never felt the need to get a membership. But that was based on my "old" perception of the lounges where it was "pancakes in the morning, soup in the afternoon. ho hum" These new offerings do sound pretty good.
Actually flying in F out of SEA (miles, not upgrade) in a couple of weeks, but a very early flight so depending on when we get through security (even with Save the Space) we may have time to check one out depending on our Gate (hopefully not N).