We enjoyed our stay at Marcella's. She was very helpful and flexible with the check-in, as well with check-out. The apartment is as described in the site, full of character and charm, and it has all you need to enjoy your stay in Rome.
The apartment is perfectly located, very close to Piazza Navona, Panteon, not far from Saint-Peter, etc. For us this was the most important, so we did not mind the noise from the busy piazza during the evening (moreover, the apartment is equipped with double-glass windows).
The apartment is clean, and you have plenty of brochures and books with information about restaurants, museums, activities to do in Rome. This was also very useful.
I totally recommend Marcella's apartment.