Great location, especially for an introduction to Rome. Walking distance to all the major sites. Piazza di Spagna (Spanish Steps) are two minutes one way and Trevi Fountain is about five minutes the other.
Villa Borghese is nearby, as is via Venuto and other trendy parts of Rome.
Easy access, too, to the subway and Termini train station.
Hotel is quaint and clean. Yes, some of the rooms are dark, so ask for rooms lower than fourth floor, which has the smallest windows.
Breakfasts are good and geared to North American crowd with cereals (with cold milk), pastries and yogurts. They'll even serve North American-style coffee, but go for the Italian stuff. Much better.

We stayed here in mid-October and we not impressed at all. First, they told us they didn't have our reservation and because of that would have to put us in the top floor. This room had a very low ceiling, and only a 2 x 2 " window and was hot, stuffy and cramped to say the least. When we entered the room, it had not been cleaned since it's last occupant. Despite numerous requests to be moved to another room, they would not budge. I wanted to leave and find another hotel but stayed on at my husband's request.

We just returned from 4 days at the Siena Hotel. It was perfect. The location was right in the heart of old Rome, easy walk to most attractions, or the metro. The room was good size with updated Bath. Clean & nicely decorated. The staff was great. Italian style breakfast with Latte's every morning. I would definitely recommend this hotel & would definitely stay again!

Stayed at the Hotel Siena over the holiday weekend 22-25 april. We booked well in advance and the hotel came very highly recommended. Arrived very late due to late arrival of Pendolino from Milan and were clearly given worst rooms in hotel. My daighter's single was ok but instead of a double bedded room we were given a minute, dark corridor-type room with two very small singles placed end to end. The room stank of cigar smoke - even the bed linen and bath towels.
When we complained we were told we could look for another hotel if we wished - this was the weekend of the new pope's installation with half a million pilgrims camping out in Rome! Breakfast was another trial we had to queue for 20 minutes for a table. What was meant to be a very special weekend was almost ruined by this disappointing hotel with very unhelpful desk staff.