Franco's apartment is an excellent location - it's literally a few minutes from some of the best tourist sights in Valletta, including St John's Cathedral, Upper Barrakka Gardens, and the city gates. It's also surrounded by a variety of excellent restaurants, museums, and within minutes of lots of shops. Valletta is a compact city, easy to explore on foot, and this apartment is in the perfect spot. I was there for four days and didn't use the ferry or bus services, but again, they are within a few minutes' walk of the apartment and would be easy to access. It was especially convenient for me because I have CFS/ME and so require regular breaks between activities - it was therefore easy and practical to return to the flat inbetween outings to different places to rest.
The apartment has plenty of space for one or two travellers, and has a mixture of conveniences (TV, wifi, kitchen for cooking) and traditional features (gorgeous old windows, balcony, gorgeous traditional tiles). I visited in early October and with daytime temperatures in the mid 20s, the flat remained cool and comfortable. For a small fee, Franco also arranged for me to be greeted and picked up at the airport and brought directly to the apartment, which was very helpful.
The only recommendation I would make is to bring ear plugs if you are a light sleeper and are sensitive to noise - like I said, Valletta is a compact city, and I did awake to occassional traffic noise in the early hours and some people enjoying themselves on a Saturday night. Certainly not a major issue - and some of the early morning sounds, such as church bells, are really lovely.
Would definitely recommend to solo travellers and couples looking to explore and enjoy Valletta and the surrounding cities.