An absolute gem! For a very low price one gets a four-star hotel type of service.
The flat is furnished with everything one would have at home (we appreciated the kitchenware in particular), including appliances, for those who want to do everything themselves. On the other hand, the apartment is of a hotel-like quality, making you feel like you really are 'on holiday'. Most importantly, it is very modern, squeaky-clean and bright. The ceiling fan is great for hot summer days. Do not let yourself be discouraged by the couch/bed - the mattress is very comfortable, feels like a normal bed.
There is really nothing we would have had differently - the flat itself is gorgeous, the location convenient and the host very accommodating and always there to help. As a local I can also say that this airbnb really is part of the 'fair-play', good kind of tourism services in Prague.
11/10, would come again :)