Marco's place is absolutely fantastic. The property is clean, modern, and wonderfully situated. We walked to everything from it aside from Vatican city for which we got the Metro.
Marco's brother met us outside the apartment and showed us round and he was really nice. He also sat us down and took us through a really helpful map in the apartment, describing the key attractions in Rome and giving us really useful information about transport and also a large book full of recommended places to eat.
The place was great; air con was a dream, the shower was nice, and having a Nespresso machine was awesome too! It is so well situated (as said above), that we were able to go out all day and pop back to shower, change and chill for a bit before heading back out. It was also in a really safe part of town which was reassuring.
We stayed for 4 nights but wish we'd stayed longer. If you're looking for somewhere cool to stay in a great location, book it.