Our family (Mom, Dad, two teens) stayed at Residence Candia for 4 nights in March, 2009. We decided to stay at the hotel because of the "three rooms apartment" which we assumed was two bedrooms and a sitting room. It was actually two bedrooms, each with "double" (between king and queen) beds, and a third bedroom that was so tiny the entire floor was taken up with a smaller, full size mattress (on the floor), which was in seriously bad shape. Additionally, there was another sleeping space in an upstairs loft, where our son ended up sleeping, and thought was great.
The apartment had two bathrooms, which was wonderful, but no laundry facilities, which were listed as in the hotel. The space was clean, but the mattresses were hard, and the lack of any common or sitting area was strange.
There were several groups of high school & college kids staying in the hotel when we were there, who were quite noisy into the wee hours of the morning. I finally went out and asked them to keep it down, and they did respect my request, but you might want to ask if any groups of students are booked there while you are there.
The staff was really nice, and the hotel was very convenient to the metro, but not overly convenient for walking to most of the non-St. Peter's sights. But, for the money, it was a ton of clean, basic space.