I took my girlfriend to Malta for her 30th birthday treat, and we stayed in Alberto's place. I really couldn't have asked for more from my first AirBnB experience.
Alberto was exactly the sort of host you need - efficient, friendly, and accommodating. He also picked us up and dropped us back to the airport (for a fee), a very helpful addition.
Believe the pictures, the apartment is exactly as you hope it will be. Simple but attractive decor, clean, and a stunning view. Breakfast on the balcony is a real treat when enjoying the harbour scenery.
Of course you'll want to see Valletta on your trip, but I'd also highly recommend eating in both Senglea and Birgu (across the water as you see it from the balcony - 'Osteria.Ve' is a great restaurant).
The ferry to Valletta is great, only a 7 minute walk away, and runs until late at night (midnight I think).
Thank you Alberto and all the best for the future! :)