I can absolutely recommend staying at Gigis place.
Not only is the flat in a perfect location (right in Brera district, so you have wonderful restaurants near and in a short walk you are at the Castello and at the Duomo!), but also Gigi was one of the nicest hosts ever!
She had some friends over and one evening we ate together. She always cares about you and if you are feeling fine and tries to help. Also, when I had problems with a late check-in (which was my fault) she made sure to have a friend over so I could sleep at her place. Whenever I come back to Milan, I would definitely try to book at her place again!