We were a party of 4 middle aged couples and this property worked really well for us. All the bedrooms are spacious and each couple were able to have their own bathroom. The beds were comfortable and we didn't have any problem with noise, although ear plugs were supplied, which made us slightly worried! You could just hear the sound of music from the piano bar several floors below, but you had to listen for it. There was enough room in the lovely lounge to cook breakfast (as is our tradition when we are away!), eat and socialise together.
The location is brilliant and gave us easy access to Princes Street, the Royal Mile and various venues for the Fringe. I would definitely recommend this apartment.
As one last point, there is currently work going on in the communal stairway, this didn't disturb us but it did mean that there was no light in the stairway when we came back late at night. Make sure you have a torch on your phone or take a small torch out with you.