Most features roll out to IAD second, third, or fourth. PDX and CMH are good candidates for earlier feature rollout, and usually it's tested in a small region first. I use PDX (us-west-2) for almost everything these days.

I also think that they've been making a lot of the default region dropdowns and such point to CMH (us-east-2) to get folks to migrate away from IAD. Your contention that they're encouraging people to use that region just don't ring true to me.