Karel is a great host, we had perfect communication and during my short stay he (and his wife) gave recommendations on things to do and places to visit, he even have maps and information, and the best was that they lend us their bikes (but Prague is not a very bike friendly yet).
The flat is lovely, perfect for short and long stays, with everything you could need.
I will definitely recomend this place and would be back if I could.
:)