We stayed in Marcia's apartment for 4 nights and absolutely loved the place. It's perfect for 2 people. Apartment has everything you need - AC, fridge and even washing machine. Not to mention how beautiful the apartment is - it looks exactly as on photos.
Marcia was working on the day we arrived so her mother and cousin welcomed us. Though we don't speak any Portuguese there were no problems. Marcia ever prepared some welcoming gifts for us! Later she was always checking is we're alright and if everything is good. We felt very welcomed during all our stay and liked Marcia and her family very much.
I think Marcia's apartment is the best place if you want to stay in the center of Rio. It has a good transportation to all the major touristic points.
But there are two things you should be prepared for staying there (in Lapa): homeless people all around the streets and some noise during weekends.
All in all, we are very happy with our choice to stay in Marcia's place.