We had a great time at Peggys house, it was a huge contributor to our great Athens expirience.
The house is few meters (literaly) from the Metro. The square is full of usefull and diverse shops and the house is very well equipt (you will not miss anything). Rooms are big and comfterble and the balciny has nice view, and very pleasant for eating at.
One point to consider is that the squere can get a bit noisy at night. but it can be easily mitigated with the windows.
bottom line : highly recommended.