I booked a superior room at the Relais Pierret for 1 night to visit Rome with my 5 year old daughter this July.
On arrival, we were slightly disappointed to find we'd been 'upgraded' to a suite in the Internazionale Domus, which is located above the Relais Pierret in the same building. I felt the standard of furnishings wasn't as good as that in the Relais Pierret, especially in the common parts. However, I have to admit that this was more than made up for by the amazing view from our window. The Spanish Steps were beautiful when empty in the morning - I've never seen them like that before. I had been concerned about soundproofing on the Steps' side of the building, as I was travelling with a young child, but noise from outside was not a concern at all - the double glazing was very effective.
The only slight problem was noise from other guests returning to their apartments in the evenings - the management really need to encourage people to be considerate when they are in the shared areas of the property, as the wooden floors and high ceilings ensure that other guests will be disturbed by noise. Otherwise, I found reception staff incredibly helpful and the car they organised for me on the final day was fabulous - really a 5 star way to see Rome!