Really nice flat, we stayed during a very hot time and the A/C was really appreciated. The kitchen is nicer than it seems in the pictures, it can get hot as the a/c is downstairs but this never caused any issues.
The host was very communicative and easily reachable whenever we needed anything.
Location is good as it's about a 10-15 minute walk to central Valletta and there's also a nice little park just a couple minutes down the road with a kiosk which is lovely in the evening. There's a little convenience store just outside the apartment building as well as a fruit and veg mini market also about 30 seconds away so between them there is pretty much everything you could need.
The rooftop is a nice bonus and there is a washing machine and dryer at the top as well. The only thing I would be aware of is that it can be a little noisy in the mornings as there's a main road quite close - but I am quite a light sleeper. My boyfriend wasn't bothered at all.
Overall, I would definitely recommend a stay at Marc's, it's central with good amenities!