I would definitly recommand stay at Sandra&Mitch's house.
They were very helpful - not only professional but also kind - we felt that they want us to feel like special guests at their house. Gina, who welcomed us at the house was also doing everything to make our stay pleasant and trouble-free.
The street and the area around is calm and quiet - and, all in all - is only 10 minutes to Metro Station and 20 minutes to Collosseum!
Their house is very comfortable and well organised for tourists - we were there with group of five - and we didn't felt like house was to tight. Kitchen is fully equipped.
And - last but not least - AIR CONDITIONING - especially during so hot summer in Rome - it is great convenience.
The Casa Felice is really happy place to be.