In one word, awesome. Just flew PDX-PAE-PDX yesterday. The terminal is pretty much full from 11:00-3:00 when most of the midday flights leave and the whole thing has a lounge like feel. My flights had super light loads (<20 people), however my Lyft driver said he heard that there were plans for expansion (terminal expansion + bigger planes). No way of knowing where he heard this. If they do grow in popularity, they will have to expand as the current terminal, while very nice, is quite small.