My father and I had an Excellent stay at the Harbor House. The location is ideal for exploring Valletta, the nearby cities, and accessing the bus system. there are many options for restaurants and grocery shopping within the city, and you are right next to the Barrakka Gardens.
the Flat itself is very comfortable, has excellent views, and the small kitchen has pretty much everything you need in order to cook for a couple of people. There were many towels available for us to use, but once it was time to do laundry there is a small laundromat a couple of blocks away. And lastly, since it is a bit colder in February, the air conditioners in the living room have a heating function that comes in very handy.
Joseph was extremely responsive; both of us forgot our keys when out on a walk one day, and he was at our door to save us within an hour! he also picked us up from the airport.
Bottom line, we recommend this place and will be returning ourselves quite soon.
P.S. take a look at the trash pick up schedule so that you do not forget to bring it out in the morning, at 7 am!