Mario & Florence's apartment is a great place to stay in Marsakala. The apartment is enormous and would easily accomodate 5 or 6 people with plenty of space. The rooms are light and airy, with very effective aircon.
The location is good, overlooking St Thomas bay and literally a couple of minutes walk from the beach. And it's about 10 minutes walk in to Marsakala itself (unless you get lost in the winding streets like I did!). Although it's on a street corner, up on the 4th floor it is quiet and nice to watch the world go by from the balcony. (There's a lift, so don't worry about hiking up to the 4th floor). There's a bus stop right outside the front door, with buses to/from the airport (2 euro - about 30 minutes) and lots of other places around Malta.
The kitchen could be a bit better equipped, but then I guess most of us don't do much cooking on holiday. Its a slight shame that the public areas of the building are looking a bit tired and run down.
Communication with Mario and Florence was great and Florence met me when I arrived to show me round the apartment and was happy to give ideas of places to visit in the area.
Overall a good value, large apartment in a good location in Marsakala.