I really enjoyed my stay in Zak's apartment! I was here for nine nights as a solo traveler and found it very comfortable and well-accommodated. The location is quite central, only a couple of blocks from restaurants, shops, the main bus terminal, and the Sliema ferry. And Zak was a super helpful and communicative host!
Note that the apartment is up a set of stairs and that this area of Valletta is hilly, so it might not be the best choice for people with mobility issues.