Good place to stay, from my experience anyway.

My three 'issues' were that I couldn't easily find the button to turn off the Tango music in my room (now there's a major complaint for you..) and the pool on the roof is small (but what pool on a roof isn't?) and the free internet is slow to clunky.

And that's it. Damn.

BA is wonderful and so is the hotel. If I had roller blades I could have re-enacted Starlight Express and skated round my room. Clean, quiet, helpful and pleasant staff. An excellent base.

Fabulous building and décor. Super location in the old part of town.
Once we had placed the suitcases on the floor of our room there was nowhere to put our feet!
As the hotel wasn't full we were moved into what they called a suite but we called a larger room. The price difference for a suite was about £15.
The larger suite was comfortable but the staff attitude left a bit to be desired.

The idea of a hotel that had it's own dance school was something different and the concept of a beautifully restored Art Nouveu home in Bohemian St Telmo was the perfect venue choice for my 60th birthday celebration in june 2010.
The hotel is very muched focused on Tango and the teachers were both friendly and could TEACH and we both could do the basic steps at the end of our short stay.
In addition to classes for guests there was also an open Milonga on the weekends that was open to the public.
So even if you dont want to learn tango it's still a great hotel to sample the elegant bygone era of BA.

Upon arrival we weren't that impressed, the room we originally checked into was small, on the main floor next to the reception area (noise), had insufficient space to 'unpack' both our bags and a TINY bathroom. Howevere, it had a stunning floor to cieling stained glass bay window we loved but still asked if we could move. Thankfully another more spacious room was available on the second floor just above the recepetion desk. It was noisy in the mornings and had no outside window but we were comfortable and it was very clean and well appointed with antique furniture. Both the rooms were equipped with a volume dial to control the flow of tango music played throughout the hotel, which only added to the unique character of this place.
All four gentlemen on staff at the front desk were helpful with directions, recommendations etc... but each one went above and beyond; Cristian helped us order pizza, Mauriano made us tango show reservations, there was an older gentleman who worked the overnight shift that helped us find somewhere to eat after 2am and Daniel, who made the nearly impossible happen when he acted on our behalf in calling around to arrange a private driver to take us to see Pearl Jam in La Plata was very kind and always willing to help.
The breakfast buffet was good, though usually picked over by the time we got around to eating, and we weren't aware eggs were available until the last day.
Dandi Mansion was conveniently located close enough to a subway, main intersection for taxis or within walking distance of plenty of great options; San Telmo is full of spots for food, drink, photos, culture and antique shopping. I'm happy we decided to stay here despite there being plenty of other nicer, more modern accomodations available in other areas of BA.