I was told by a friend that the Alvear is as fabulous as the Ritz in Paris, for half the price. I don't know, because, unlike my friend, I did not stay at the Ritz when we went to Paris (though our hotel there was quite lovely). I do know that the Alvear is world class and just stunning.
The hotel is in a very upscale neighborhood (the entire city is really very pretty), and is within easy walking distance of good shops and restaurants (though cabs are so inexpensive, location does not matter much in BA).
The lobby is pretty, with lots of marble and pretty fabric. Our room was just perfect. It was very pretty, with large closets (including one cedar), the bathroom was large, complete with a stand alone shower, jet tub, and Hermes toiletries. And, our beds were the best I've ever encountered in a hotel. The fresh roses and daily fresh fruit were a nice touch.
The staff was helpful, friendly, and not obtrusive. We enjoyed evening drinks in the lobby bar, which came with warmed nuts and other complimentary nibbles. We did not have time to try the restaurant, though did enjoy the breakfast buffet, and afternoon tea - more food than the two of us could possibly finish.
We spent only four nights in BA, and nearly cried when we had to leave. The city is so interesting, that we spent a lot of our time out and about (including a day trip to a ranch - such fun), so didn't get to spend as much time just enjoying the hotel as we might have liked.
The hotel is just opening a new spa - in fact it was not open while we were there, but a sweet employee took me on a tour (my request), and I will definitely have some services the next time I am there.