We stayed at The Planet Apartments back in March 2014 for a short break in Reykjavik. The location of the apartments is very good being in Walking distance of the main centre and lots of lovely restaurants are nearby. The apartment we had was in the style of a large open plan studio with a big comfy sofa and comfy bed. The heating and showers were very good (the showers do smell of eggs\sulpher because of the way the water is heated for some buildings in Iceland but you get used to this).
If you want to cook for yourself there are plenty of supermarkets in walking distance and the apartment has a fully equipped kitchen with cooker & dishwasher.
The young lady who was looking after the apartments named Diljá was super friendly and really helpful. The communication was excellent & she even went as far as to call and sort out our return bus transfer for us as they had somehow messed up our reservation.
If you're coming for a break in Iceland I'd recommend you stay here!
Restaurant tips - I highly recommend a visit to Fiskfelagid (Fish Company), Glo and also Saegreifinn - The Sea Baron.