Portland probably changed more in the 17 years between 1989 and 2006 than in the 18 years between 1971 and 1989. You couldn't film a movie set in "Portland, 1989" these days without some serious effort. The skyline has changed too much, and the trademark neighborhoods (the Pearl, Hawthorne) are too clean.
Portland used to be gritty. It was really gritty in 1971, and it was still gritty in 1989. I remember driving down Burnside on Thanksgiving Day, 1995 and thinking "there are a lot of prostitutes in this town".
In the featurette, Gus Van Sant and all the other behind-the-camera people are walking around in the rain without Gore-Tex. In 1989, fancy Hollywood people wore rubber rain coats (just like fishermen!) when making movies. North Face, et al. had not yet realized the market potential of $200 rain wear.
I really miss the Thrifty Scotsman sign at the old Thriftway on Glisan. This is now a Trader Joe's. You can see the sign in a corner of a shot in the scene where the gang robs the old Nob Hill pharmacy.
The Weinhard's brewery is visible in most exterior shots in the last act. When I first moved to Portland in 1998, I lived on Johnson near I-405. Most winter and spring days I had a pretty good whiff of that brewery. It smelled like oatmeal or yeasty bread most days, but some days it was a little more like the floor of bar. Memory is odor. To me, "Portland" smells like used books and that warm, yeasty, oatmeal smell. ("Oregon" smells like pine trees and coffee. "Eugene" smells like a paper mill and pancakes.)