First, the flat itself is *fantastic*. Beautiful, great furnishings, good AC, and in a great location on a lovely street with shopping and restaurants in Milan. If those are the only things you care about then this place is great.
However, the check-in was the worst we experienced in 3 weeks in Europe. You HAVE to download the custom "Sweet Inn" app to your phone and use it as a digital key. Even then the whole process it get into the flat is incredibly confusing. It took us about 90 mins to finally get into the flat. The property description says the parking is "on the premises" but that is not correct (at least not in English). The parking is around the corner in a pay lot. Not a huge problem but we had to contact the manager to find out where to park.
The property management company Sweet Inn seems to be running their own parallel rental business and using Airbnb to find customers. They made us "register" through their own web site including paying a "deposit fee" which was equal to the entire rent. They claimed it was a "security deposit" but it just went as a charge straight onto our credit card. The charge was reversed (as they said it would be) a few days after our rental ended. Just to be clear - this is not how Airbnb works. They have their own system for insuring rentals.
Anyway, if you don't mind putting up with all that stuff then the flat itself is perfectly lovely! We only stayed one night, and I'm sure if we had stayed for more than the rental friction would not have seemed so bad.