I couldn't have hardly found a better location in Valletta to stay for a few days in order to explore the city. If the canons firing daily bothers you this was pretty close (but then again it's loud for a good part of the city). The location is out of the main way by a few blocks and I had no problem whatsoever with people being loud in the streets at nights.
The kitchen was stocked though small and the host provided some bottled water and sweets. The bathroom can get musty but there's a dehumidifier in there (it's underground after all). The air conditioning worked well but the place was naturally cool.
I would stay here again and recommend it other others if they are traveling solo or as a pair. Don't miss the Chocolate District up the hill for its fine coffees and chocolates.