This is a great place for anyone who is visiting Edinburgh for a few days or longer. My two kids and I stayed for 7 days (6 nights). I had a conference at the University of Edinburgh and then we used the rest of the time for sightseeing. It was great to see the Castle outside the kitchen window (and from the two chairs set up on the balcony/walkway outside of the flat) day and night. It added to the atmosphere.
More than just how it looked, however, the location saved us tons of money since we were within walking distance from all the major sights (Museum of Scotland, Greyfriars Kirk, University of Edinburgh, Castle, Royal Mile, etc.). It is located near a wide range of places to eat since it is just a block away from Grassmarket. It is also close to a grocery store.
The flat is really nice. There is a bedroom/sitting room where there is a bed and a sofa that can be turned into a bed. There is a TV, Wi-Fi, etc. They also provide a converter so that anyone can hook in their electronics regardless of where they are visiting from.
The bathroom is quite nice (it even includes a bathtub, which isn't always the case). There was hot water (perhaps not hot enough for some American standards, but we were fine).
The kitchen has a small refrigerator so, coffee maker, tea kettle, toaster and microwave. There are pans and kitchen utensils. Patrycja was nice enough to provide us with some cakes (especially a really nice coffee cake) and biscuits (some homemade!).
She responded quickly to every email that we sent. The directions on how to get to the flat were straightforward. She was nice enough to let us drop our bags off early even thought we arrived three hours before check-in and they were still cleaning the flat.
There is construction on a building nearby, but the week we were there, the noise was not a problem at all.
Definitely a gem! If we head back to Edinburgh, we will check to see if this flat is available.