From the privious guests' comments, I was expecting a friendly host living in a pretty place, and that was exactly what we got! In fact, the house was even prettier than I'd thought, full of characters and charm.
Now looking back, I think we made the right decision staying in Mdina rather than Valletta. Coming from and leading a hectic life in the biggest city in the world, having a walk in the evening in Mdina couldn't have been more special. We visited Valletta pretty much every day, but it wasn't far at all anyway (20 mins by cab / 30 mins by bus).