Our experience was overwhelmingly positive. The flat itself looks great, you can tell it was redone not so long ago. Very spacious, for a family of 4 there was plenty of room. Great kitchen which we used extensively for cooking. The 2 bathrooms/ showers are also nice to have for so many people. Considering that we have stayed in worse and more expensive places, this really was a great apartment.
The hosts themselves were very, very nice and accommodating. They were kind enough to pick us up and drop us off at the ferry. They always responded to any questions or requests we had, it was just lovely interacting with them.
Qala itself is a very nice, small village. For those just looking for a quiet holiday, it's great. A few small shops, bars, restaurants and the beach serve that purpose quite well. People were very nice in general. Traveling around Gozo was easy with the public transport, and the ferry was also 20 min by foot or 7 mins by bus, so the other islands were easily accessible.
A few drawbacks:
For a small village, there is a quite a bit of traffic going down the roads that run along the flat which unfortunately make it somewhat loud. Not for the light sleepers, though ear plugs helped us with that. Also, as indicated, the beach isn't all that close, maybe 20 min by foot, and uphill on the way back. The walk itself it quite nice though, you can even go more closer the the coast, away from the main road.