We have stayed at Marcos apartment for a couple of days while we were visiting friends in Rome. It was very clean and comfortable, and even though via Ostiense is a busy road, very quite, because the apartment is facing the river. The pictures on are very accurate - we got what we expected.
Also for exploring the centre of Rome, the apartment is conveniently located, just a few bus or metro stops away.
The only negative points were related to the communication with the hosts. They were in general a little unresponsive - before our trip we, we received the check-in details quite late, an earlier request for information was ignored; during our stay we asked for an additional blanket and didn't receive any response.
Despite these downside, we had a very pleasant stay and I would recommend the apartment any time.