My partner and I stayed for a few days at Marit and Dominique's place. It was a great choice, within walking distance of Valletta itself. The place itself is fairly small, as described, but well appointed. We didn't miss anything and we enjoyed the huge bathroom as well as the coffee machine.
The Floriana neighborhood was a great experience. It's close to Valletta, though keep in mind the heat and sun in summer can make this a tougher walk than it appears at first glance. There isn't a ton of things to do in the neighborhood, but there's a convenience store, a cool café within walking distance (La caffetteria Siciliana), a really good bakery (Tad-Dulcier), and a really super-cool bar with cheap drinks and plenty of local character (Vilhena Band Club).
We really appreciated Marit and Dominique's local guide! I've never seen this in another Airbnb rental, and it gave us a great local insight into places to visit and restaurants to try. Definitely worth checking out. I also have to commend Marit and Dominique for their fantastic reactivity.
One thing I have to mention, for those who have mobility issues, is that the (gorgeous) bathroom is in the basement, which implies climbing downstairs to get to the bathroom. The bathtub, which you can see in the pictures, is absolutely gorgeous, but be aware that it requires some balance to use as a shower. If that's not a major issue for you, then by all means go for this place.
Overall, a very positive experience at a good price. We appreciated being a bit removed from Valletta, with the possibility of experiencing Malta as locals. Thank you Marit and Dominique!