I was to Milan for 3 days and Cristina was nice to let us stay at her appartment. She was away so we had all the appartment just for us (we like privacy).
When we got there we there was a bottle of wine on the table for us and a paper with all the information anyone would need (about house and things that you might use, AC, washing machine, coffee machine etc). The place itself is very nice, even if it seems small in pictures, is not. There's plenty of space, very good arranged so you have access to all you might need. We had TV, AC, Internet, hot water in the shower, fridge and some goodies for breakfast, coffee machine and all that you would need if you want to cook something.
The place is at maybe 6-7 min from metro, on a normal walk. To get at Duomo, you only take one metro, same for coming from Central Station.
I would definetly recommend for others to talk with Cristina and book her place if you want a trip to Milan.