Went in 2012 - loved it. As mentioned ^above, it doesn’t necessarily have a tick list of must sees that other cities have but rather is just a wonderful city for walking, eating and drinking. That said, BA has the most theatres of any city in the world apparently, so it’s definitely worth taking in a show while you’re there - tango and opera the obvious choices.
We stayed near Retiro, which is very central and meant that we could walk everywhere. Would recommend brushing up on your basic Spanish as very little English spoken by anyone. They are still dealing with the after effects of the early 00s economic collapse so cash is king - we were regularly offered 15-20% discounts for paying in cash rather than on card. Annual inflation runs at around 40% so hard to say how affordability has changed since we visited, but it was relatively affordable. We took a stash of US Dollars to change up while there - pretty much any bank will do this for you, but due to currency controls the process is quite long winded. You literally need to fill out all of your personal details and provide your passport to change up cash.
One interesting thing is the British influence out there. Around 1900 there was massive British investment in Argentina, so you can still see Victorian design in loads of the infrastructure. Also surprising was just how much currency being English was while we were out there - we were there during the 30th anniversary of The Falklands/Malvinas war so expected things might be a little touchy. On the contrary - when people found out that we were English they literally could not have been more interested to talk to us or more welcoming. A weird dichotomy (do not mention The Falklands though obviously).
Are you just visiting BA? We spent a month in Argentina so could recommend other sites if you’re planning to travel. Also, are you flying Iberia? Worst. Long Haul. Airline. Ever if so. Pack your own food, drink, entertainment if you’re going with those clowns.