Carlos is a very nice and friendly host. He always responded to questions (before and during the stay) pretty much immediately and was very helpful with tips, such as restaurant recommendations.
The location of the apartment is great - interesting neighborhood with good restaurants and very close to both metro and tram. Using the metro you can reach the Duomo in under 15 minutes (including walking time from the apartment to the metro station). Alternatively you can use the very beautiful tram (tram stop directly in front of the house), which takes a little bit longer but you can see a lot of the city and the tram-ride is a little bit of an experience by itself.
The apartment itself is quite spacious and very clean. We were there as family of 4, but you could easily stay at the place with 6 (or probably even 7 or 8) people. And we were welcomed by a nice bottle of wine :)
Can recommend Carlo's apartment to anyone visiting Milan!