Firstly, the location in Grassmarket is fantastic. There are lots of restaurants and bars nearby, and it’s a short walk up to the Royal Mile.
The flat is neat and tidy, and is best suited for two people travelling together. If you have a third person and use the sofa bed, there isn’t much space left over for luggage ... it’s OK for a few nights though.
The WiFi seemed a little slow at times, which was the only downside.
The decor was interesting and suited the place; the washing machine was much better than others we’ve encountered; the bathroom floor was unusual (in an interesting, positive way).
If we’re back in the area (but as a couple rather than family) we’d happily stay again.