Zak's place is extremely conveniently located to all of the sites of Valletta, some great restaurants (Guze/Legligin/Rubino all within a couple blocks), bars (check out Cafe Jubilee!), a very nice shopping area, and the main bus terminal, yet the street was still very peaceful. The apartment was very clean, great wifi, plenty of storage, and a comfortable bed. There was a hair dryer and an iron/ironing board, plus plenty of adaptors for us to use which was a nice touch.
I highly recommend arranging a taxi from the airport through Zak - our flight landed late in the evening and our driver showed up with a sign, gave us our key, and told us some information about Malta and Valletta on our drive into the city. Everything went very smoothly which allowed us to start our vacation off in a relaxed way (and it cost €18). Zak was also flexible with our check out time - he allowed us to leave our packed bags in the apartment until we had to go to the airport for our late flight. (I assume this is only possible when someone isn't checking in the next day.)
The only minor negative thing was the low shower pressure - but I think this is normal for most places in the area, just a heads up.
I definitely recommend Zak's place without hesitation!