The staff is very helpful, and a big part of their menu is gluten free (and marked gluten free). Just make sure to let them know that you have coeliac, and they'll take care of any cross contamination.
I've had some of the dishes that are not marked GF, that the staff has changed for me, and it has always been great. The flavour has never suffered for the slight alterations that had to be made.
We arrived just when the restaurant opened, which was good because we got to order and recieve our food quickly. The waiters were nice and when we asked about the menu they made sure to double check with the kitchen. We ordered a 3-course tapas meal. We changed the grisa taco with a vegan taco because of nut-allergy. The tacos were small, but oh how delicious they were. The main course was beef with chimchirri and aji amarillo. The beef is the most tender I have eaten in my entire life, and the dish itselft was so well balanced. The last dish was a chocolate mousse with vanilla ice cream. It had some hard sprinkle of chilli, a special sort of onion and some unknown. It was a good way to end our dinner. In addition to this we ordered drinks. I talked to the waitor and he was so kind that he made me my favorite drink even though it was not on the menu. We also got a glass of wine on the house. We forgot to tip the waitors, it is not possible to do so by card, only in cash. We will definetly come back here the next time we are in Iceland.I am one of those who notices gluten immediatly when I consume something, even in very small amounts, but I had no trouble here.