I was going to attend a two-day meeting and called Hotel Regina for reservations. I was told to confirm my request through email, and I did it. Right after, I received an email confirming my reservation and the fare.
Once I got there, after a whole day of meeting, around 7 PM, I was told there was no reservation for me. I don't use to print anything unless it is explicitly marked as necessary, so I didn't have the printed copy of that confirmation email. I suggested I could show them right there on the front desk computer, then the woman in charge, called Maria, ended that conversation in these (or equivalent) words:
"There is no room available, even if you show me any paper. I suggest you walk two blocks in that direction and try to find a place in another hotel called...".
First: they seem to have no control over the reservation process;
Second: they did not allow me to check my email and show them I had a reservation;
Third: in total lack of professionalism, the attendant "suggested" that I started walking in search for another available room somewhere else.
What else can I say? Don't run that risk, there are plenty of good hotels in Rio.

We stayed in Regina for an overnight in Rio and were very pleased with the clean and comfortable rooms. A great choice for families as they have quad rooms.
Excellent breakfasts.
Contact the hotel directly if you are booking last minute, we got a great deal.

Hotel Regina is a good option if you are looking for value and simply need a decent place to sleep after touring the sights. The hotel is located in Flamengo, which appeared to be a fairly nondescript area of Rio, but has access to the beach acoss the road and is well served by public transport links (subway and bus) providing good access to the centre and to Copacabana and Ipanema. The breakfast is ample and well replenished. Staff are helpful and obliging. If you do not require glitz and simply need a clean and safe place, this hotel is a decent bet.

Stayed for three nights in July, found the staff friendly, the rooms basic, clean, and comfortable. Good value, included a great breakfast. Wifi in room is NOT free, but relatively inexpensive. Close to the subway and Flamengo beach. Will require either taxi or use of public transit to see the sights. They'll organise tours for you.