We had a great time at Charles place. The flat is located in a calm area with the sea at walking distance (5mn), convenience stores at 2mn and the bus stop just down the road.
The self checking was smooth with good indications and we were welcomed with some drinks and things to eat (which is a great plus when you arrive late at night) :)
The flat was clean and everything was working perfectly.
We also had some recommandations from Charles (good restaurants and places to go) which were really helpful.
If you want to go around and visit Malta in a very short time, I would advise to have a car as the bus can be a bit long depending on where you want to go (20mn to go to Marsaxlokk, 45mn to Valletta).