If you're into Tango, or more bohemian, or from the US, you probably will like Buenos Aires.
But I see it much like I expect Canadians see the US: something like my home city (Montevideo), with both the good and (especially) the bad things magnified.
There are beautiful parts of Buenos Aires (I recommend Recoleta and Palermo), and lively parts of Buenos Aires (not my speciality :) ), and they're both nice.
(I live in Montevideo, Uruguay which is quite close to Buenos Aires)