My wife and I stayed a weekend in Rome at the beginning of Dec 2008. We read many reviews here in TripAdvisor, and we couldn't decide. Eventually we set our mind on La Fenice. It turned out to be a great success.
The rooms were very nice and it seemed that renovation has been done not so long ago. The water was hot, the service and courtesy of the staff was great. There were about 4 different receptionists and all were helpful and friendly.
Breakfast at the roof balcony was good as well. Excellent cappuccino...
Last but not least - LOCATION!
This hotel is pretty quiet and very central. Few blocks from the Trevi fountain and the Spanish steps.
We'll certainly come back again.

I stayed w/my wife for 2 days and, while she was in the hotel the day before (for works), i arrived the day after (for holidays). The room she booked was a double but not so big, so we asked if it was possible to stay in a bigger room and kindly they give us the "Michelangelo" suite room, a bigger room with a beautiful view on Roma. Each one passed from the reception desk was pleasant w/us. The place is 2 min. walking distance from Piazza di Spagna, so a 15/20 min walking distance from the main monuments of the Ancient Rome. For all the other places in Roma (Vaticano, Basilica di S.Paolo fuori le mura, etc..) there is the metro station at 1 min. A little minus sign regarding breakfast (not a very rich breakfast, but croissants, ham, etc. was present) and regarding the spaces and the bed in the rooms in the main hotel building (but for a 2 days holidays is enough).

I stayed in the La Fenice Hotel for two nights in May. Overall, the hotel was okay but was not particularly great value for the money. The front staff were friendly and helpful with one major exception (more on that below) and the rooms were okay, but not great. The location is good for a first time visitor to Rome as it is very close to all the major sites (the Spanish Steps, the Colliseum, etc.) but I don't think I would stay there again. I prefer the area around the Vatican as it is quieter and generally more cost-effective.

The breakfast was not great at this hotel - the "juice" was chunky and weird tasting, there was hair on the cheese, which looked old, the meat tasted funny and the bread was stale.

As I mentioned above we had one major issue with a front-desk employee. The afternoon before our departure, we went to the employee, who was an older gentleman, and asked him to please book us a car to take us to the airport the next morning. The hotel had a big sign at the front desk saying that they would happily book you a car for just this purpose, just let them know the day before. He refused and said that it was "too expensive" and that we should just take a cab since they are cheaper and it would only take five minutes to get one in the morning. We had our doubts, but against our better judgment we allowed him to talk us into it. So the next morning we go down and ask for a cab, and of course it took awhile to get one (close to 25 minutes). We are so lucky that traffic wasn't too bad or we would have missed our plane. So if you want a car and this guy argues with you and tells you to take a cab, say NO and DEMAND that he book the car!

I stayed here for two days for a work-related event. The rooms were all right. They could probably have been classier (that's my taste) but they contained the things that you'd expect from a four-star establishment (tv, minibar, air conditioning, ...)

Wireless internet was available for a small daily fee. Breakfast was standard hotel fare, and the staff was friendly.

The hotel is a bit off the city center, but the staff will help you with the transport. They also sell bus tickets.

There is a nice courtyard/garden for the guests to use and some couches and meeting points where you can sit down and talk.