This is a great place to crash when rolling through PDX or staying for a few days, but mostly out on the town. There is more than enough space for a two people to come and go (who don't mind sharing a bed). There is a kitchenette for storing snacks and drinks and some minor food prep, plus a little table to sit at. The couch isn't made for lounging, but the big, super comfortable bed is.
There wasn't constant noise like loud music or yelling and whoever lived upstairs clearly tries to be conscious of noise. That said, you'll hear them walking around sometimes and/or coming in and out of the shared side door, and the washer and dryer can be heard just outside of the unit door.
Though it's a basement, there is a large window that lets in a good amount of light during the day. Because it's a basement, the air is just a bit damp. It does not smell of mildew so I don't think the moisture gets out of control.
Re: accessibility, note that coming down into the basement the ceiling is very low so you'll need to be physically able to bend down while coming down the stairs. Not an issue for most people, but probably helpful to be aware of for some travelers.
The neighborhood is beautiful for walking, with some restaurants and other businesses within walking distance (good food and coffee). You can access many parts of the city easily via car.
Overall, the unit was very clean and well decorated. The bathroom gets a slightly lower rating on cleanliness, but it certainly wasn't filthy.