Theres like 5 or 6 rooms in this huge apartment which is converted into a B&B with individual bathrooms. The neighbours are all residents. The owner is only there in the morning unless you specify. Every room is given 3 keys, 1 for the room, 1 for the apartment, 1 for the main entrance. The place is very clean, with a kitchen for breakfast(locked for rest of the day) and a tiny fridge in the main area. Our room is very spacious with 1 queen bed and 1 single bed and a TV. The whole place is not carpeted which is fine by us. The owner is very friendly and tries to help whenever you asked. It is a street away from one of the stations and bout 3 streets away from the Termini.
Cash prefered for payment. While a bed at a hostel cost 25euros with shared bathroom, we find ours wonderfully cheap and fulfil the basics at 70euros.

Excellent location, cozy and clean rooms, friendly owners.
Although we did not speak Italian and the owners spoke very little English we understood each other and got very good service.
Principe is located not far from Termini railway station which makes it very convenient for travellers. Main Rome's sightseeings are not in a walking distance (however good walkers as I am don;t think so! :-)
Breakfast is not huge but well enough.
The only disadvantage was that the airconditioner could not always cope with the hot Roman weather.

It's a perfect location if you need to be at Termini station early in the morning. We would definitely stay here again! We stayed here by recommendation from a travel agent in Florence and we were quite pleased. Reading some of the unfavorable reviews has been surprising because we thought the B&B great! Very close to Termini, just a few blocks walk and the B&B was impeccably clean. Victoria is an angel and we felt so very well cared for during our 2 night stay. The neigborhood is not the most pleasant but I also don't feel it is unsafe.

FLEXIBILITY
We arrived at 9 at Termini and we could check in at 9.30 and even have a shower before going on tour. Victoria provided us with a city plan and basic orientation and gave us an insight in how the city transport works.
When we wanted to leave early to visit the Vatican Museums, it was no problem to serve breakfast at 7 o'clock and we could even take something with us to eat on the go.
On the check-out day, it was no problem to leave our bags in the appartment and return to collect them in the afternoon.

FRIENDLY ATMOSPHERE
Victoria likes to chat (we did this in Spanish, her English isn't very good) so we learned many interesting things at the breakfast table. We felt like being her children (her son is in fact the same age as me) which was very nice in most cases.

LOCATION
5 minutes from the Termini station on foot. This is a great plus! You'll have to take the tube to get to the major sights, but as the B&B is in the very centre of Rome, you get everywhere in a matter of minutes.
People from all around the world live in this part of the city, but we felt safe, even when returning after midnight.

ROOMS
Very nice and comfortable, with free internet access (WiFi or classical LAN - which is faster). Equipped with taste. We would have preferred carpet instead of tiles and we didn't like the fact that our double bed turned out to be two beds put together.

BREAKFAST
OK, but would be terrible if you should stay longer than 3 nights. There was no cheese (only spread cheese), no ham or salami and no fresh bread. There were synthetically tasting muffins, the cheapest toast bread, jam, honey, "yoghurt" and some corn flakes. The juice was terrible. If you like abundant breakfasts with a nice espresso (which you won't get here) - and need that during your Rome stay, choose a different place to stay.