I had a pleasant stay at Karl's apartment. It's only about a 7 minutes walk from the city gates in the center in a nice residential area. The bus stop is just up the road (in case you are not traveling by eCab); and generally speaking you will find most of what you need in the vicinity.
The apartment was clean and instructions on how to get there were clear. It's not a big space but everything you need for a few days is there and it wasn't an issue for me at all.
For what I paid I'm very happy with my stay and will surely consider staying at Karl's apartment again if I visit Malta sometime in the future.