An upside of Marco's apartment is certainly the great location. The apt is in the heart of the historic center of Naples, at a comfortable walkable distance from all major Neapolitan landmarks. Also, Marco and Antonia are really kind and available to help you with anything you need, which I truly appreciated.
A downside is that the apt smells like mildew. Like the majority of Neapolitan "bassi" (https://visitnaples.com/neapolitan-bassi/) the apt is really small, dark, and humid. Yet, it is equipped with AC and a dehumidifier that works really well, which you may need to keep on for a bit before going to bed since the bed (rounded but comfortable) is on the ground floor where it's most humid.
When it comes to services, I found the apt very little equipped in terms of kitchen supplies, the majority was visibly overused and some even broken; there were neither a bin nor bags for the trash/recycling; there was something yellow at the bottom of the water boiler, so I couldn't use it; the sofa upstairs is super thin and uncomfortable; and, unfortunately, the apt was not thoroughly clean (something I told Marco and Antonio, who promptly reimbursed me the cleaning fee.)
In sum, great location, great hosts, the apt in itself needs some maintenance, though.