I can't imagine a much better location as your base in Prague. Wonderful river/castle view from the living room (shame the windows are small), walking distance to all major sites and transportation. Spacious and clean rooms.
We mostly had breakfast in the apt with food bought from Tesco (about 10min walk), etc., but there was a nice bakery opposite from the National Theater, only a couple of mins walk from the apt, that was very nice for breakfasts as well.
We had some trouble with the check-in timing in the beginning, but they were easy to communicate with via email (thankfully we had mobile internet connection even before we got the WiFi pwd from them..otherwise, this might have been a much bigger issue).
As for the beds, our kids took over the bedroom and the main bed, and we sadly had to sleep on the pull-out sofa. The mattress was not exactly high quality on that, so if you have back problems, you'll need to sleep on the main bed.
All in all, an excellent stay. We'd definitely return here if we found ourselves in beautiful Prague again!