I stayed at this beautiful and spacious flat with a friend a couple weeks before Christmas and we both couldn't have been happier with it. It was perfectly located. From the flat we could walk everywhere we wanted to go, with the exception of the castle, which we hoped on the tram for, located just a few feet from our doorstep. This tram is also well connected to the city and makes it easy to arrive by train (as my friend did) or via the airport (as I did).
Also, Mark was a wonderful host! He gave us so many tips and recommendations... I especially liked the restaurants and coffee shops he recommended. The were all very good, reasonable, and not touristy. As we stayed for about five days, Mark also gave us great suggestions for less touristy things to visit. He was also very easy to reach if we ever needed to. And the flat itself was lovely too! It's very spacious and has a full kitchen, if you fancy some meals at home.
All in all, if you're visiting Prague, I'd highly recommend staying at this flat! You won't be disappointed!