We stayed at Sergio's apartment in November. There were two adults, a four year old and a baby. Sergio provided a baby cot and baby seat too, which was really helpful.
It's in a really good location, just a short walk from the bus stops to get to the centre - takes about 20 mins to the main sights. The Colosseum is an easy walk too, in 15 mins or so. There are a couple of small supermarkets nearby if you need to stock up on essentials.
Testaccio is a cool neighbourhood, the food market is great if you're self catering, and there are some nice restaurants and takeaway places just minutes from the apartment.
The cake shop around the corner (Pasticceria Barberini) was amazing - definitely buy the cakes by weight, as you'll end up with more of the amazing patisserie treats, and they're surprisingly good value too.
Amenities were all good, although the heating is centrally controlled in the block so we couldn't turn it on, and the aircon was not working either. This made it quite tricky to dry clothes (we were rained on a fair bit!) and the wash we did on day one wasn't dry three days later! Without the glorious Rome sunshine we couldn't dry our towels either.
Overall I would recommend a stay at Sergio's apartment for couples and small families visiting Rome.