The communication with Paul prior to arrival, and Marcine while we were there was perfect. Everything was arranged as promised, as well transport, and there were no surprises (at least not the negative kind). The area was nice (close to the Sliema ferry, good playground, and, of course, central Valletta itself).
If you have small kids with you, like we had, you can use your luggage to create a 'gate' that prevents them using the spiral staircase. That would definitely be necessary, since spiral staircases are deadly by nature.
Air condition was sufficient to cool down the apartment after being turned off the whole day, helped with fans.
I'm sorry, but I can't think of a single negative. For us everything was perfect.