The upside: Excellent location right in the heart of Valletta, extremely nice hosts, a beautiful old building, a nicely set-up room, a really large and comfortable king-size bed (this was the main attraction for us), perfectly clean, good A/C.
The downside: A bit cramped, no door for the toilet, only an electric curtain (there is nothing the host can do about it, I assume), no shelves for clothing, etc. (this could be easily fixed). And the room can get very noisy at night and in the morning. Outside the main window, there is a square with a cafe, and if the outside tables are full, it sounds as if people are sitting in your room. It would help if the windows were somehow reinforced to offer some sound protection.
Overall: A very nice place to stay in Valletta, but not perfect.