My wife and I wanted a quality hotel within easy walk to the city center and convenient for bus tour pick-ups. We also wanted the hotel to have a restaurant, king-sized bed, and large bathroom. After reading lots of reviews on TripAdvisor and other sources, we chose the Marina and had an excellent stay of 4 nights.
When reading other reviews of 4 and 5 star hotels in Reykjavik the main issues that seemed to have popped up over and over again seemed to be "hot" rooms, small bathrooms, and lots of noise interfering with sleep. So when we booked the Marina, we booked a "King Junior Suite" on the 4th floor (their top floor) on the harbor facing side of the hotel furthest away from their ground floor Slippabarrin bar/restaurant. We also booked our stay in mid-September so that we would have darkness during sleeping hours. We lucked out and got it right.
You can read other reviews about the "quirkiness" of some of the hotel features, but this is simply a very nice Scandinavian-flavored hotel. The staff is excellent, the breakfast (which we had included with the room rate) was fine (but not great); there is an ATM from an Icelandic bank in the lobby for currency exchange; and the "Blue Bus Stop" (for tours and airport transfers) is literally right outside the main entrance. There are numerous restaurants within a short walk and even more if you are willing to walk out of the harbor area closer to the city center. We arrived much too early for check-in, and stored our bags in the reception closet area. We then bought their breakfast buffet and ate real slow! Afterwards, we checked on our room, and the person we spoke with gave us a map and suggested a walk around the city, which we did and enjoyed. After we finished our 2 mile walk and visit to the big church, we sat in the lobby and our room became available just before noon. That gave us just enough time to get our bags up there, wash up a bit and make it to the Blue Shelter for pick up for the 1 PM Lava Tour. Back that evening, we ate at the delightful Italian Caruso Harborside which is perhaps 300 feet from the hotel.
Back to the room: The room had a king sized bed that was comfortable (I have a bad back and had no problems); a love seat sized couch, a chair and stool and night tables. There was a coffee machine in the room which we did not use; the coffee that comes with breakfast in their restaurant was far too good to turn down. The closet is "open style" with hangers for clothes that need to be hung and space for a suitcase and some shelves. It included a safe. We left the other suitcase on the floor in a corner near the couch and still had plenty of room. The room also had a balcony that overlooked the working harbor. The bathroom was more than adequate for us, with a rain-down type shower and a big wooden sliding door for privacy. The room itself was never that hot, but for sleeping purposes we sometimes would open the balcony door for a while to cool it down a bit and we always left the window open, even while sleeping. In the spring/summer leaving the window open at night might be a problem for some as to get air from the window you have to leave the black-out curtains partially open. But that is why we chose mid-September for our trip when it got dark about 7:45 PM (and light about 6 AM). The hotel seemed full during most of our stay but we heard no noise either from our neighbors nor from outside.
We were away from the hotel most days as we booked several tours with Nice Travel. We liked that we could wait inside the hotel in a seating area directly opposite the Blue Bus stop for our pick-ups. We found, by accident, that Nice Travel picks up at the Marina first, so we were able to get our pick of seats on their mini-buses.
On our last day (Saturday) we took a long tour of the South Coast and did not get back to the hotel until after 9 PM. Exhausted, we simply went to the Slippabarrin restaurant and found it to have friendly service and an empty table for us. I had the "fish in the pan" (the fish that day was a Ling filet) and my wife had a flatbread. We both thought our food was delicious and well served.
We loved our stay at this hotel and would do so again without any thought. However, note that this hotel has several room types and some are (according to other reviews) small and/or over the bar or face the busy and at times noisy road on the opposite side of the harbor. We were told we had one of the largest rooms in the hotel and it was ideally located (#436).

Hotel in retrofitted paint factory couple of blocks from the Marina. Small rooms and sparse appointments. Small bathroom with no tub.

Ok to stay overnight but not much beyond just a plain hotel that serves the basic needs - clean and comfortable.

Friendly staff and good breakfast.

My husband and I stayed three nights at the Marina hotel. The rooms are simply but comfortably appointed in Scandinavian style. Everything was clean and working well.

Bathroom is a little quirky in that is is a corner of the room with frosted glass partitions dividing it from the room. But bathroom itself was fine and shower great.

The hotel is well located in the harbor area. There are a lot more shops and restaurants in the area now than when we visited four years ago.

Breakfast buffet offers a lot of options. The one dinner we had in the hotel (group dinner) was average. I wouldn’t choose to eat dinner there with so many good options steps away.

Staff was friendly and helpful. However, the hotel is very poorly set up to check people in efficiently. On our second checkin at the end of our trip, we had to wait half an hour to check in because of systems issues and their not having adequate staff.

Besides this, we had a good experience.