We spent a very nice weekeend in Edinburgh, the apartment was greatly located, well equiped and very clean. The code system is also really great and convenient when travelling in a group !
The one major down point, that is NOT a detail, is the very poor quality of the beds (springs matresses), and worst : the brown sofa bed. It is absolutely not suited for guests. It is collapsed and extremely uncomfortable. You can barely sleep and wake up with neck and back pains. The last night, we even slept with the matress directly on the floor. It was hard but more confortable than the sofa itself.
As a result, the appartement is not suited for 6 people but only 4. It's a shame because Carol is a great host and the apartment is very well equiped and central, it was perfect other than the very uncomfortable beds and the nightmare sofa, but good sleep is important on vacations... I would definitely recomend the apartment if the brown sofa is replaced and eventually the other matresses as well ! If you barely sleep or don't mind at all, it's a great place ! :)