I booked one night here because they say they are 800m from MXP, and I have a 6 AM flight from there, heading back to the US. Any advice?
Their website says the shuttle starts operating at 5 am, so check if they can get you there earlier. I don't believe there will be any flights direct to the US, so this must be a connecting flight. In that case, you should get there 2 hours before departure. You may have to have them arrange a taxi.
If you could change your reservation to the Sheraton Malpensa Airport, you wouldn't need to worry about a shuttle. The Sheraton is a part of Terminal 1 at Malpensa.
Thank you for your replies! I don't want to have any room for error at 6 am. I did change to the Sheraton.