Hi there. I visited buenos aires august for 3 days, not really much to see IMO. Did the tango and dinner show and visited gaucho ranch, ate at a churascharia (sorry if I spelled it wrong) resto and went for a city tour (just a drive around the city. Best part of our trip was when we took a flight to puerto iguazu, we booked at sheraton (hotel inside the park) to see iguazu falls (argentina side). worth the money and effort Argentina is not really cheap and I'm not really interested in shopping there. btw, don't forget to try dulce de leche ice cream, yum!
Must eat steak, if you are meat eater, it's was like butter. Best steak ever.
Visit Recoleta (sp), you can see where Eva Peron is buried, when you are looking at her marker, you are standing on her grave. And as previously mentioned try the dulce de leche, amazing!