Both good and bad to report. On the plus side, the main room is spacious and attractive. The wood floors are quite nice, views from the fourth floor are nice, as well. Overall, it looks better from the inside than it does when you first enter the back door of the building. The owner, Solvi, provided a multi-page package in advance that was very helpful in setting out where to find the key, area attractions, etc.
On the down side, since it is on the top floor of a gabled building, the walls angle inward quite severely. This is particularly acute in the bedrooms, where I hit my head more than once (OK, that's my fault after the first time...). A thorough cleaning of shelves & cabinets would help. The bathroom needs renovation, and the washing machine makes enough noise that you'll think it is going to come apart. (It didn't.) There is no dryer, but there is a drying rack that worked fine. One note of caution - since Iceland gets its hot water from geothermal springs, it is HOT! Start the shower with the hand-held pointed against the shower wall and adjust the hot water in tiny increments to avoid scalding.
Now for other things the owner has no control over - the neighborhood had occasional nighttime noise (actually less than expected). There are two large construction cranes a block away, one of which had powerful floodlights on all night. Blindfold and earplugs were needed.
Expensive for what you get, but overall it was OK,