This is a great B&B if you are visiting Rome and need a central location with modern/clean accommodations. The building is a bit of a non descriptive office building in which two floors have been converted into hotel rooms. The rooms are Ikea type furniture, laminate flooring, very modern style bathrooms. Over all the place is VERY clean and very well maintained. The manager, Ronnie, was amazing and extremely friendly and helped us with whatever we needed.
The location cannot be beat (especially for the price we paid). In the heart of the city and close to all the historic sites. You're given vouchers for breakfast at the cafe located next door -- voucher entitles you to a coffee/drink and a pastry.
The B&B does not have any other frills -- ie no pool, fitness room, etc. There is a local gym within walking distance that I used, called Linea Fitness (http://www.lineafitnessclub.it) but be warned, it was expensive ($20 Euro per visit). For those obsessed with working out, this is a viable option and can be a justified expense given the savings of staying at the Relais Chigi! :)
Back to the room itself, we were lucky to have the only balcony in the building which was great for people watching. The only issues we had were: 1. We ran out of hot water a couple of times but we were told that the tank would reheat within 30 minutes; 2. The A/C was a bit of an old unit and wasn't very powerful -- although it was positioned to blow on the beds so sleeping was comfortable (if not freezing) but during the day the unit wasn't amazing to cool the whole room.
In summary, over all, a great location, great hotel, good value (we paid $140 Euro/Night), and clean place to stay while in Rome.