Stayed here for 4 nights in March 2008 (also in the Jockey Club room, like the previous reviewer.) The owners are very nice people and were available 24/7. They speak English and are also very patient if you want to practice your Spanish or ask questions about Buenos Aires.
The owners prepare a fresh breakfast for you whenever you want it. You can take it to your room or eat in the living room or up on the roof terrace. The terrace and the entire building are pleasant and attractive.
Unlike the previous reviewer I did not find it loud; there is just oridinary urban background noise, and Calvo is not a particularly busy street.
Location is great, San Telmo is safe with lots of shops, restaurants, bars, etc. It is a safe and easy 10-minute walk to the Plaza de Mayo.
I had no real complaints. Water pressure in the shower was weak, but this was a minor issue, and it is to be expected anyway in an old building.
Altogether, a good choice for lodging, and the owners help to make it an especially pleasant stay.
One final note: The electric outlets in my room were the kind with two small round holes, similar to Europe. If you bring the wrong adapter, you can buy one in a cerrejeria shop or from a street vendor for 2-3 pesos.

This is a new B&B in an old house. We had the Jockey Club room, which is the only one on the top floor of the house, with private bathroom and balcony. The house is a bit old and the owner is renovating it a bit, so don´t expect all new stuff. The room was nice, but it was hot and with lot of noise from the street. But that´s to be expected when you´re staying downtown ofcourse. The other rooms downstairs where more quiet I think, but may have more noise from neighbouring rooms.
The owner speaks English and is very helpfull with everything. You can also use his computer whenever you want.

I stayed at the Four twice during the month of October 2007. This is an unusual hotel with a gifted host, actually a couple with two wonderful children who have converted an old house into a beautiful bed and breakfast.
each room is different. the service is unusual because it is personal, the breakfast is great, with fresh peach juice. you may have to wait a bit because everything is cooked to order.
clean rooms, great views from the terrace which is on the roof. highly recommeded.