Carla's apartment is huge, very well-lit, and super equipped. We really enjoyed having access to the extremely-well-equipped kitchen and it was great to have a clothes washer available. The apartment has a great plan and you could easily have two couples staying here with no problem (though one bedroom is open to the rest of the apartment, on a mezzanine, and the other has a door) or a family with a couple of pre-teens or teenagers.
The internet connection was very good, I was able to do some work and make some Skype calls with zero problems.
The location is great, you won't hear too much traffic noise, but you will definitely hear people talking loudly on the street at night, especially on the weekend (but that's what ear plugs are for).
The location is fantastic and really central, we didn't even use public transportation, we just walked everywhere (including the Vatican, the Colosseum, Testaccio, and Trastavere).
Highly recommend a stay in Carla's apartment!