We didn't get to meet our host in person but he was very helpful during the organization of the trip. A maid was awaiting for us at our arrival and she kindly explained everything there was to know about the apartment. We just had to make one phone call to setup the WIFI: during the rest of our stay we never needed to call the owner again.
The apartment is a basement flat and this is clearly stated in the announcement: therefore your windows open on the reasonably quiet streets and it feels more humid but also more fresh than the scorching outside.
The location is simply perfect to explore Malta. The zone seems safe and it is reasonably quiet. It is near 2 large and a small supermarkets. It is very near the sea (you can see it as soon as you are on the street) and some rocky seaside that is perfect for children because there are like small inner pools where they can swin safely. It is also near pharmacies and a private doctor that visited us on the first day for just 13€! It is also very near the bus line that comes from the airport and you easily reach in ten minutes walk the Sliema Ferry. You can have wonderful walks during the evenings and if you feel like walking, in 90 minutes of brisk walk you can even reach Valletta. All this, alone, already makes the apartment really advisable.
The apartment is quiet, wide, clean and well equipped. There are some nice objects around that makes it feel nice but we had to move them out of the way to avoid the children break anything.
There are laundry machine and tumble drier and they work ok. Beds also were OK. Fortunately there was also a socket adapter for our mobile chargers that use different plugs from usual maltese one but it's better to carry an adapter from home. The owner also provided us with several instructions and map and offered to arrange for us the trip from the airport to the apartment.

To recap: if you don't mind a basement flat the apartment is really valid and advisable for a week visit to Malta.