It was our first time to use Airbnb and we were very concerned. It was also our first time to visit Malta. Reserving this appartment online was very easy, especially with the help of Ian. Getting there was even better; His parents recieved us, showed us the appartment in details, and even took us in their car for a mini tour. The appartment itself is not huge, but great. Everything is brand new, even the building itself, and you have there anything you will need. Ian and his parents are great and were there for us whenever we needed them (I think they live close). Security wise, I think you'll have nothing to worry about in Depiro point.
As for the location, we thought it was perfect. It was very close to St. Julians, but not too close to be noisy.