The apartment was clean and comfortable. Perfectly suited for a family of four (though we had 5 and didn't struggle to find space).
The highlight of the place was the location: one block from Laugavegur, filled with restaurants, shops, and a short walk to major sites, museums.
Parking was a little bit of a challenge since the road it's on is P1 parking (the most expensive option), which was the only negative; While I got lucky and found a free spot at the school by Hallgrimskirkja and left it there for a couple of days, P3 parking is only a block away and fairly cheap (by Iceland standards) if you can't find a free one.
In general, would very much recommend this place for visiting Reykjavik.