My wife and I stayed at L'Hotel Cinquantatre for a week in early November 2008. The location is great, less than a block from the Barberini metro station and a taxi stand, and walking distance to central Rome. We got a good package rate with airfare. Our room was a superior double on the back side of the hotel on the 5th floor. The hotel was fairly quiet, except for some early morning noise from the breakfast room one floor above. The bed was comfortable, and the room was fairly up to date (including lots of electrical outlets for recharging gadgets). The room was a bit larger than we expected, a pleasant surprise. The breakfast is fairly basic: one kind of cereal, yogurt, some rolls, croissants, and cheese, coffee and tea. No fruit. Overall we thought the hotel was a good value, and we had a pleasant stay.

One important caveat: the hotel web site (lhotel53.com) claims that internet access is available. This is incorrect, there is no internet access provided by the hotel (although they claimed that they would provide internet access in the near future). Check before you book if you need internet access, or check for access points near the hotel.

Good hotel with a central location near Barberini metro station (good connections to Termini etc.). The area (financial district) where the hotel is situated is perhaps not the most exciting in Rome but it's quiet (relatively speaking) and safe. The room was basic but clean and the staff helpful and friendly. The breakfast was served on a roof terrace which had a nice view over the neighbouring rooftops. The breakfast in itself was ok, typically Italian, so don't expect a huge buffet.

Small hotel on quiet side street near busier Piazza Barberini and 15 min walk to Fontana di Trevi. Restaurants and shops are nearby, but look for Internet in other neighorhoods.. Room was typical
European size (small for american standards), but it was all we needed. Our room had a separate room for the toilet and bidet, instead of in the bathroom. A small tv was located in the closet.

Breakfast was served on the top floor on their outside rooftop patio. There are only 3 tables outside so we ate inside once when it was at a busier time. The breakfast lady was very nice and helpful. Only a few slices of bread and cereal, no cheeses/meats or American breakfast.

The location of this hotel was perfect. It was within easy walking distance of the Trevi Fountain, Pantheon and Spanish Steps and with the metro being at the bottom of the road it was a short underground ride to the Vatican and the Colloseum.
The reception staff were very helpful and always pleasant.
The rooms were clean and plenty big enough. We stayed in 102 which as mentioned by some others has an 'odour' coming from the bathroom. As the room was mainly a base this didn't bother us too much. Also a spray of deoderant cleared it quite quickly.
The rest of our party stayed on upper floors and had no such problem.
The breakfast was pleasant with options of croissants, rolls, cereal and yoghurt, with tea/coffee and juice. Breakfast can be eaten on the balcony or indoors, and the walk up to the top floor certainly wakes you up for the day ahead!
We also made the most of the top floor balcony for illicit evening drinks! There is no serving bar, however the nearby supermarkets selling Peroni at ~£1 for a pint was much cheaper than the local bars!
Would definitely stay there again, just avoiding room 102.