I stayed at the Regno with my mum for 4 nights over New Years, after booking through a travel agent, and found it to be exactly what we needed.
Had a minor issue with our room upon check in. After checking in early, we were advised that a room was available, but found that this was a double room, rather than a twin (which we had requested). They happily showed us another room, which had a double bed and a fold out bed. We stated that this would not be acceptable for a 4 night stay and they showed us a tiny twin room. We asked for the double in the second room to be separated, which they did. This probably means we ended up with what would be classed as a triple room.
The room itself, on the thrid floor, was very comfortable and clean.The beds were brilliant and we had plenty of space to store luggage and hang washing. The bathroom looked recently renovated, with a shower, toilet and bidet. We had no problems with hot water, although found the water could not be kept on full pressure (which was excellent) for an entire shower as the alcove would flood. I agree with a previous review in that the linen, includeing towels was exceptional.
Breakfast was provided and was always more than enoughy to carry us through to dinner. A selection of pastries, cold meat, cheese, yoghurt, cakes and toast was offered, along with a small selection of average tasting fruit. The breakfast room oozed ambience, with a glass ceiling, which was very convenient to check weather conditions, especially in winter!
The staff were helpful and some were very friendly, with others always courteous. They were more than willing to help with directions and supplied us with a great map of Rome upon check in. Storage of luggage was also not a problem.
The position of the hotel was fantastic. We walked everywhere, apart from the Vatican (although it probably could be done). There was also a great little restaurant down the alley leading to the Pantheon, which served fantastic food at very reasonable prices. There were bus stops 5 minutes down the road and tobacconists for bus tickets the same distance away.
The only real negative was the busker that would plant himself opposite the hotel every night and sing the same song on a loop for hours. He was always finished by the time we anted to sleep, but was there enough that we knew the chorus of his song word for word and were seriously considering what we could throw out the window! ;)
We found this hotel to be charming, comfortable, pretty much as we expected and deserving of a 3 1/2 star rating. We'd absolutely stay there again!