1. The most realistic speed is actually 186mph (300kmh) max making for a ~90min trip between Seattle and Portland - which is still great.
2. There's a completely alternate alignment for a good chunk of the Seattle-Portland distance (former Milwaukee road branch lines and the old chela is western). There is also a rebuilt alignment of the old Tacoma western that will just went in service that will cut 30min off then trip from Tacoma to Olympia anyway.
3. Interestingly, it shouldn't be thought of as a mid-distance intercity train. It's a commuter train at higher speed. In Japan a huge number of people commute on the Shinkansen. Imagine if you could commute in 20min from Everett to Seattle or Olympia to Tacoma.