We were a group of two couples and a toddler who stayed at Julia's place over Christmas. The locations is AMAZING! Doesn't get better than this. It's right by the Old Town Square, but far enough away that it's quiet. It's easy to walk to everything and to catch public transit (it's super easy to get to the airport, and inexpensive, so I'd recommend it over an airport transfer or taxi). There's no elevator, which was a bit of a challenge with the stroller, but not a deal breaker.
The flat is very large - there's a nice big common room and kitchen table, which worked well for us. The layout is a bit strange, with one room opening onto both the living room and kitchen, but it was fine in the end. There's only one shower, but it's separate from the other bathrooms so it was easy for everyone to access and use.
The downside of this place is the amenities. A small investment could make a big difference in the overall experience. Some simple upgrades to bedding, towels, pillows, and kitchen tools/utensils would make the space more comfortable and usable. We managed, but were a bit surprised given how great the flat is otherwise.