The location is probably the best one can find in Prague. Quiet and at the same time central. Very secure and with many and various restaurants and coffee shops around.
The apartment is spacious and very clean. A bit old but with modern bathroom and kitchen. Drainage and water pressure in the shower are excellent. The shower has the usual one-quarter of a circle configuration one finds in many renovated Prague apartments, that may be a bit narrow if the person is very large. The gas heater, with which I am accustomed from my own home, makes some adjusting noises, nothing to worry about. The kitchen appropriate for limited cooking activity, but for visitors is a perfect solution. The heating during winter was more than adequate; I had to open the window some time to cool down the rooms. The bed was very comfortable. The 4th floor offers spacious view of the sky and provides abundant day light; a set of transparent curtains could be a nice addition.
The hosts were professional. In three occasions they were fast to respond and solve the issues: they provided a desk top table for my lap top, the sent me instructions how to use the washing machine and they took action to increase speed and stability of the internet wi-fi, all three the next day after requesting their help. Check-in was a breeze and they allowed me a couple of hours more staying on the departure day.
I will definitely try to stay again in this apartment in my future visits at Prague.