Ondrej's apartment is in brilliant location, walking distance to all the main attractions. We arrived early, but the reception staff of the hostel let us use the luggage store and gave us a map with recommendations where to go, which was much appreciated. The apartment is small but has everything you might need. Only thing we didn't like were the towels which have seen better days. They were worn off, and thin. Not very nice to use.
Nonetheless, the apartment is a nice base for exploring Prague.