Initially when we walked into the apartment we were disappointed. We had expected bathrooms to be ensuite in a 'luxury' let but they weren't. However this turned out to be not too much of a problem.
The pros of the flat are its location - superb, the size of the beds and the general spaciousness.
The cons are the shoddiness of the decorations, pictures on the walls are cheap and falling apart for example, an extremely poorly stocked and appointed kitchen and the general drabness of the apartment - it is bare and unwelcoming. Also one of the bedrooms faces the Royal Mile and is consequently extremely noisy 24 hours of the day - it needs secondary glazing.
Having said all this, we are considering renting the same apartment again as the wonderful location makes up for all its drawbacks.

We stayed at City 12 for a friends 40th birthday, it was a lovely apartment with great access to the city, perfect for a group of friends wanting to celebrate together. The only downside was the squeeky doors, a squirt of oil or WD40 would be helpful!! Everything else was perfect!