We had a great stay at Relais Colonna. The room was exactly as advertised, and it was so nice to be able to relax in the jacuzzi bath after walking around Rome all day.
Gianluca was there when we checked in and he gave us loads of advice on where to go, what to see, where the best views were, etc.
The location is really good. It's only a 10 minute walk to Vatican City, and about 40/45 minute walk to the Colosseum. Our Uber from Roma Termini station was €10.
The pizzeria just across the street is amazing (Salvatore di Matteo). One of the best pizzas I've had in Italy. There's also a great gelato shop a 5 minute walk from the relais (Neve di Latte).
I would definitely stay there again next time I visit Rome.