This has always been a puzzle for me. The local papers run articles on coffee in Buenos Aires, but always leave out:
Establecimiento General de Cafe!
When I lived on Santa Fe y Aguero, I discovered Est. General de Cafe on Pueyrredon and Arenales. Their coffee matches any I've had anywhere (and I'm a coffee exagerado from way back). I'm not familiar with the trendy shops in Palermo so can't compare them, but for me, when coffee's as good as it can get, I don't need to look elsewhere.
It's expensive, to be sure - very expensive by just about any foreign standard. But as we know, any quality imported good is spendy here, so it's not a surprise. What continues to confound me is that I've never seen the business in any list of Best Coffees in Buenos Aires. That, I don't understand.