This apartment worked well for our family of 4. It is located within walking distance to many sights, shops, restaurants. There is a food market, bakery, park, and public pool all within an 8 block radius. A main road is 3 blocks away that connects to Highway 1, as well as the route to KEF airport.
The unit is clean and well furnished, with ample room for 4 people. There is a washing machine if you need one. Parking is on the street, but we never had trouble finding a spot close by. The owner met us personally at the unit for checking in, and he was flexible in allowing us to check in a little early, since we arrived on a early AM flight. I can list only two minor annoyances: 1) the apartment is on a one way street, and due to road construction, it was a slight challenge to get to it. 2) A relative "heat wave" in the city made for warm conditions inside in the evening as there was no fan.
I would highly recommend this apartment and I would stay there again when I visit Reykjavik in the future.