I stayed here for two nights and absolutely loved it!
The hotel itself is only one floor of the entire building, so it's very small but this adds to its charm,as does the modern decor. Rooms aren't amazingly big, but they definitely aren't too small either, and they are equipped with everything you need (tea/coffee making facilities, good sized flat-screen tv) as well as being modern, very comfortable and clean. And the bathrooms, although fairly small, are absolutely spotless!! Breakfast, as has been said before, is basic, but there is still plenty to fill up on and the continental buffet is constantly being refilled before items run out.
The hotel is run from another building, but is looked after during the morning/early afternoon by an attendant. Although she speaks very little English, she is very friendly and made a big effort with us.
As the hotel is not manned all the time it means if you arrive late there may not be anyone in the building to let you in, however this isn't a problem. We arrived in the evening, but just called the phone number on hotel sign outside the main door and were promptly let into the building remotely.
The hotel is in a fantastic location, very close to Termini station, walking distance from the main attractions (eg. Colosseum, Trevi Fountain) and the beautiful Basilica di Santa Maria Maggiore at the end of the street.
Will definitely be staying here on my next trip to Rome!