We highly recommend Marco's. The place provides high value, specifically when it's your first time in Roma. You can be sure you won't make a mistake.
Important observation :
we went there in november. We don't know how it is in full summer...
Cap (Miss' comments ;)
Location :
The place is easy to access by underground. It is not in the very historical center of Roma, but it is only 15-30 min away from most historical places. There are also bus lines. The flat itself is at a walking distance from the underground (5 min)
Host :
We didn't meet Marco one on one, but Marco was highly reliable and definitely responsive through airbnb message box (often less than 5 min) whenever we had to get in touch.
He made us easy to drop our luggage when we arrived even if this wasn't the right moment for him.
The Flat :
Kitchen : fitted open kitchen fully equiped (washing machine, oven, etc.)
Living area : big room, light, with long balconies
Bedroom : big bed, very comfy, rolling shutters (which is pleasant when you prefer sleeping in a dark room ), huge closets.
Bathroom : confortable, with a shower and the toilets
Other equipment : washing machine, flat iron, etc.
Pay attention : as Marco warns, there is an extra local tourist tax (for us 28 euros/ 4 nights)
Yann ( Mr's comments) :
I would add that :
the flat is bigger than it looks like on photos
it makes you feel secure : good building and neighbourhood, armoured door
it is very close to a big green area (Villa Lazzaroni),
there are simple traditionnal (and less touristic) restaurants in the area
the location gets you out of the crowded places, which is refreshing when you come back after a long day with other tourists,
for tango dancers (as we're) there is a great milonga (the Must) in Anagnia (end station on the same underground line)