We had a great time at Dario & Bea's flat.
My wife and I try to travel a lot so to not sound repetitive with reviews we try to divide them into basics:

1. The Essentials:
Good Neighborhood (feels safe even going out at night). Clean beds and a clean shower. Train 5 minutes away. Solid Wifi. Attentive Host.
The agreed fee charged (70 Euros) is fair because the apartment is a great value. We just wish it was put automatically somehow into airbnb.

2. The Extras:
The neighborhood is not very vibrant, but it is very safe and really close to train (Manzoni). The distance to the colisseum depends on how fast you walk. 10 minutes for my wife and I. 15-20 minutes for our 62 year old companions. There are a couple of great restaurants near by (Pizzeria Luzzi and Li Rioni a Santiquattro had great prices and really good stuff)
We would definitely stay here again!!

3. Tips for other travelers:
The Church around the corner (San Giovanni in Laterano) is a little Gem so make sure to check it out. The nearest station, Manzoni is perfect for going to the Vatican Museum and Termini. As of December 2014, fontana Trevi is under repair so that is a bit of a downer but you can feel better by going to Il Gelato di San Crispino two blocks away. Best, Gelato, around.