Firstly Josef (the host) is very helpful and efficient. The apartment is really nice and modern in an old building. It is clean and well laid out. It is on the 3rd floor but serviced by a lift. Everything you should need is in the apartment.
We found the location ideal. It is about 25 mins walk from the Old Town Square and also from the Castle but the trams go by right outside if you prefer not to walk. There are 3 stores close by and the restaurants/pubs are cheaper than those in the Old Town but still as nice.
Finally, I highly recommend using the airport transfer service on offer. Otherwise you may have to use tram, metro and then a bus to get to the airport.